Inertia Measurement Device, Vehicle, And Electronic Device

ABSTRACT

An inertia measurement device, which is used in combination with a satellite positioning receiver that outputs a positioning result at every T seconds in a positioning system equipped on a vehicle, when a Z-axis angular velocity sensor, a position error P[m] based on the detection signal of the Z-axis angular velocity sensor while the vehicle moves at a moving speed V[m/sec] for T seconds satisfies Pp≥P=(V/Bz)×(1−cos(Bz×T)) (where, a bias error of the Z-axis angular velocity sensor is Bz[deg/sec] and a predetermined allowable maximum position error during movement for T seconds is Pp[m]), and a bias error Bx and By of the Y-axis angular velocity sensor satisfies Bz&lt;Bx and Bz&lt;By.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/295,008 filed on Mar. 7, 2019, which is based on, and claims priorityfrom, JP Application Serial Number 2018-042387, filed Mar. 8, 2018, thedisclosures of which are hereby incorporated by reference herein intheir entirety.

BACKGROUND 1. Technical Field

The present invention relates to an inertia measurement device and thelike.

2. Related Art

For example, as disclosed in JP-A-2012-251803, JP-A-2014-228489, andJP-A-2017-20829, various inertia measurement devices including atriaxial angular velocity sensor and a triaxial acceleration sensor areknown.

In the inertia measurement device of the related art, angular velocitysensors having the same specification but different only in aninstallation orientation are used for an angular velocity sensor formeasuring a roll angle, an angular velocity sensor for measuring a pitchangle, and an angular velocity sensor for measuring a yaw angle. Forthat reason, a measurement error of each angular velocity sensor isapproximately the same.

In a case where a positioning system including an inertia measurementdevice is equipped on a vehicle, there is no problem as long as requiredaccuracy for a measured value of each of the roll angle, the pitchangle, and the yaw angle of the vehicle measured by the angular velocitysensors is approximately the same. In practice, however, it was foundthat a measured value of the yaw angle is desirably higher in accuracythan the roll angle and the pitch angle.

SUMMARY

The invention is based on the knowledge.

A first aspect of the invention is directed to an inertia measurementdevice which is used in combination with a satellite positioningreceiver that outputs a positioning result at every T[second] in apositioning system equipped on a vehicle, and the device including, whena front and rear direction of the vehicle is set as an X-axis, a leftand right direction of the vehicle is set as a Y-axis, and a directionorthogonal to the X-axis and the Y-axis set as a Z-axis, an X-axisangular velocity sensor which measures an angular velocity around theX-axis and outputs a first angular velocity signal, a Y-axis angularvelocity sensor which measures an angular velocity around the Y-axis andoutputs a second angular velocity signal, a Z-axis angular velocitysensor which measures an angular velocity around the Z-axis and outputsa third angular velocity signal, an X-axis acceleration sensor whichmeasures acceleration in a direction of the X-axis and outputs a firstacceleration signal, a Y-axis acceleration sensor which measuresacceleration in a direction of the Y-axis and outputs a secondacceleration signal, and a Z-axis acceleration sensor which measuresacceleration in a direction of the Z-axis and outputs a thirdacceleration signal, and in which, in the Z-axis angular velocitysensor, a position error P[m] based on the third angular velocity signalwhile the vehicle moves at a moving speed V[m/sec] for T secondssatisfies Pp≥P=(V/Bz)×(1−cos(Bz×T)), (where, a bias error of the thirdangular velocity signal is set as Bz[deg/sec] and a predeterminedallowable maximum position error during movement for T seconds is set asPp[m]), in the X-axis angular velocity sensor, a bias error Bx[deg/sec]of the first angular velocity signal satisfies Bz<Bx, and in the Y-axisangular velocity sensor, a bias error By[deg/sec] of the second angularvelocity signal satisfies Bz<By.

According to the first aspect, since the bias error Bz of the Z-axisangular velocity sensor is smaller than the bias error Bx of the X-axisangular velocity sensor and the bias error By of the Y-axis angularvelocity sensor, the angular velocity around the Z-axis which is the yawangle can be obtained with higher accuracy than the angular velocityaround the X-axis which is the roll angle and the angular velocityaround the Y-axis which is the pitch angle. The bias error Bz of theZ-axis angular velocity sensor is a value that makes a position error ofthe vehicle during movement of T seconds which is an output interval ofa positioning result by a satellite positioning receiver equal to orless than a predetermined allowable maximum position error Pp.Accordingly, when the inertia measurement device is equipped on thevehicle as a positioning system by being combined with a satellitepositioning receiver, accuracy of the inertial navigation which allowsthe position error during T seconds, which is the output interval of thepositioning result of the satellite positioning receiver, to be equal toor less than the predetermined allowable maximum position error can besecured.

A second aspect of the invention is directed to the inertia measurementdevice according to the first aspect, in which Bz<0.5×Bx and Bz<0.5×Byis satisfied.

According to the second aspect, the bias error Bz of the Z-axis angularvelocity sensor can be 0.5 times or less of each of the bias error Bx ofthe X-axis angular velocity sensor and the bias error By of the Y-axisangular velocity sensor.

A third aspect of the invention is directed to an inertia measurementdevice used in a positioning system equipped on a vehicle, and thedevice including, when a front and rear direction of the vehicle is setas an X-axis, a left and right direction of the vehicle is set as aY-axis, and a direction orthogonal to the X-axis and the Y-axis set as aZ-axis, an X-axis angular velocity sensor which measures an angularvelocity around the X-axis and outputs a first angular velocity signal,a Y-axis angular velocity sensor which measures an angular velocityaround the Y-axis and outputs a second angular velocity signal, a Z-axisangular velocity sensor which measures an angular velocity around theZ-axis and outputs a third angular velocity signal, an X-axisacceleration sensor which measures acceleration in a direction of theX-axis and outputs a first acceleration signal, a Y-axis accelerationsensor which measures acceleration in a direction of the Y-axis andoutputs a second acceleration signal, and a Z-axis acceleration sensorwhich measures acceleration in a direction of the Z-axis and outputs athird acceleration signal, and in which, when the Allan variance of thefirst angular velocity signal of the X-axis angular velocity sensor isset as BISx[deg/hour], the Allan variance of the second angular velocitysignal of the Y-axis angular velocity sensor is set as BISy[deg/hour],and the Allan variance of the third angular velocity signal of theZ-axis angular velocity sensor is set as BISz[deg/hour], BISz<0.5×BISx,and BISz<0.5×BISy are satisfied.

According to the third aspect, since the Allan variance BISz of theZ-axis angular velocity sensor is smaller than the Allan variance BISxof the X-axis angular velocity sensor and the Allan variance BISy of theY-axis angular velocity sensor, the measured value of the yaw angle canbe obtained with higher accuracy than the roll angle and the pitchangle. Also, the Allan variance BISz of the Z-axis angular velocitysensor can be made less than 0.5 times each of the Allan variance BISxof the X-axis angular velocity sensor and the Allan variance BISy of theY-axis angular velocity sensor.

A fourth aspect of the invention is directed to the inertia measurementdevice according to the third aspect, in which BISx>5, BISy>5, andBISz<2.5 is satisfied.

According to the fourth aspect, the Allan variance BISz of the Z-axisangular velocity sensor can be set to be less than 2.5[deg/hour], andthe Allan variance BISx of the X-axis angular velocity sensor and theAllan variance BISy of the Y-axis angular velocity sensor can be set tobe greater than 5[deg/hour].

A fifth aspect of the invention is directed to the inertia measurementdevice according to any one of the first to fourth aspects, in whichBx>1140[deg/hour], By >1140[deg/hour], and Bz<570[deg/hour] issatisfied.

According to the fifth aspect, the bias error Bz of the Z-axis angularvelocity sensor can be set to be less than 570[deg/hour], the bias errorBx of the X-axis angular velocity sensor and the bias error By of theY-axis angular velocity sensor can be set to be greater than1140[deg/Hour].

A sixth aspect of the invention is directed to the inertia measurementdevice according to any one of the first to fifth aspects, in which theX-axis angular velocity sensor is configured to include Ngx sensorelements, the Y-axis angular velocity sensor is configured to includeNgy sensor elements, and the Z-axis angular velocity sensor isconfigured to include Ngz sensor elements, and Ngz>Ngx and Ngz>Ngy aresatisfied.

According to the sixth aspect, by constituting the Z-axis angularvelocity sensor with a larger number of sensor elements than those ofthe X-axis angular velocity sensor and those the Y-axis angular velocitysensor, the bias error Bz of the Z-axis angular velocity sensor can bemade smaller than the bias error Bx of the X-axis angular velocitysensor and the bias error By of the Y-axis angular velocity sensor.

A seventh aspect of the invention is directed to the inertia measurementdevice according to the sixth aspect, in which Ngz≥2 is satisfied.

According to the seventh aspect, the Z-axis angular velocity sensor canbe configured to include two or more sensor elements.

As a configuration of the Z-axis angular velocity sensor, for example,an eighth aspect adopted. That is, the eighth aspect of the invention isdirected to the inertia measurement device according to any one of thefirst to seventh aspects, in which the Z-axis angular velocity sensorincludes, in an orthogonal coordinate system including an electric axis,a mechanical axis, and an optical axis of quartz crystal, a base portionhaving a principal surface along a plane defined by the electric axisand the mechanical axis, a pair of detection vibration arms one of whichextending from the base portion in a plus direction of the mechanicalaxis and the other of which extending in a minus direction of themechanical axis, a pair of connection arms one of which extending fromthe base portion in a plus direction of the electric axis and the otherof which extending from the base portion in a minus direction of theelectric axis, a pair of drive vibration arms one of which extendingfrom each connection arm in the plus direction of the mechanical axisand the other of which extending from each connection arm in the minusdirection of the mechanical axis, at least two beams extending from thebase portion, and a support portion connected to a tip portion of eachbeam, and in which a first beam made of quartz crystal, which is one ofthe beams, extends from an outer edge of the base portion between theconnection arm positioned on the plus side from the base portion in theelectric axis direction and the detection vibration arm positioned onthe plus side from the base portion in the mechanical axis direction,and the first beam includes a first extension portion extending from thebase portion in the plus direction of the electric axis, a secondextension portion extending from the first extension portion in the plusdirection of the mechanical axis, and a third extension portionextending from the second extension portion in the minus direction ofthe electric axis.

A ninth aspect of the invention is directed to the inertia measurementdevice according to the eighth aspect, in which the X-axis angularvelocity sensor and the Y-axis angular velocity sensor are Si-MEMS typeangular velocity sensors, and the X-axis acceleration sensor, the Y-axisacceleration sensor, and the Z-axis acceleration sensor are Si-MEMS typeacceleration sensors.

According to the ninth aspect, by using the Si-MEMS type angularvelocity sensors as the X-axis angular velocity sensor and the Y-axisangular velocity sensor, and using the Si-MEMS type acceleration sensorsas the X-axis acceleration sensor, the Y-axis acceleration sensor, andthe Z-axis acceleration sensor, it can be configured at lower cost thanthe Z-axis angular velocity sensor.

A tenth aspect of the invention is directed to the inertia measurementdevice according to the ninth invention, which further includes acontainer that accommodates the X-axis angular velocity sensor, theY-axis angular velocity sensor, the X-axis acceleration sensor, theY-axis acceleration sensor, and the Z-axis acceleration sensor.

According to the tenth aspect, the X-axis angular velocity sensor, theY-axis angular velocity sensor, the X-axis acceleration sensor, theY-axis acceleration sensor, and the Z-axis acceleration sensor can beaccommodated in the container and packaged.

An eleventh aspect of the invention is directed to the inertiameasurement device according to the first to tenth aspects, in which thefirst angular velocity signal and the first acceleration signal becomecalculation reference signals for a roll angle of the vehicle, and thesecond angular velocity signal and the second acceleration signal becomecalculation reference signals for a pitch angle of the vehicle.

According to the eleventh aspect, although the roll angle and the pitchangle measured by the X-axis angular velocity sensor and the Y-axisangular velocity sensor are lower in accuracy than the yaw angle, byusing the acceleration signals of the X-axis acceleration sensor and theY-axis acceleration sensor as reference signals, it is possible toobtain the roll angle and the pitch angle with higher accuracy than acase where these reference signals are not used.

A twelfth aspect of the invention is directed to a vehicle including theinertia measurement device according to any one of the first to eleventhaspects, and a control unit that controls at least one of acceleration,braking, and steering based on an output signal of the inertiameasurement device, and in which execution or non-execution of theautomatic operation is switched based on the output signal of theinertia measurement device.

According to the twelfth aspect, an automatic operation of the vehiclecan be performed with high quality.

A thirteenth aspect of the invention is directed to a portableelectronic device including a case having an opening portion, theinertia measurement device according to any one of the first to eleventhaspects accommodated in the case, and a processing unit accommodated inthe case and processing an output signal of the inertia measurementdevice, a display unit accommodated in the case and having a displayscreen which faces the opening portion, and a translucent cover thatcovers the opening portion.

According to the thirteenth aspect, a portable electronic device usinginertial navigation can be realized.

A fourteenth aspect of the invention is directed to an electronic deviceincluding the inertia measurement device according to any one of thefirst to eleventh aspects, and a control unit that performspredetermined control based on an output signal of the inertiameasurement device.

According to the fourteenth aspect, an electronic device using inertialnavigation can be realized.

A fifteenth aspect of the invention is directed to a vehicle includingthe inertia measurement device according to any one of the first toeleventh aspects, and an attitude control unit that performs attitudecontrol based on an output signal of the inertia measurement device.

According to the fifteenth aspect, attitude control of the vehicle canbe performed with high quality.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a function block diagram of a positioning system of a firstembodiment.

FIG. 2 is an explanatory diagram of a sensor coordinate system of thefirst embodiment.

FIG. 3 is an explanatory diagram of a position error of the firstembodiment.

FIG. 4 is an explanatory diagram of calculation of a position by aninertial navigation computation of the first embodiment.

FIG. 5 is a graph illustrating an example of a relationship betweenelapsed time and an error of yaw angle of the first embodiment.

FIG. 6 is a graph illustrating an example of a relationship betweenelapsed time and a position error of the first embodiment.

FIG. 7 is a graph illustrating an example of the Allan variance of thefirst embodiment.

FIG. 8 is a graph illustrating an example of a relationship betweenelapsed time and an error of yaw angle of the first embodiment.

FIG. 9 is a graph illustrating an example of a relationship betweenelapsed time and a position error of the first embodiment.

FIG. 10 is a perspective view of a sensor unit of a second embodiment.

FIG. 11 is another perspective view of the sensor unit of the secondembodiment.

FIG. 12 is an exploded perspective view of the sensor unit of the secondembodiment.

FIG. 13 is a perspective view of a circuit board of the secondembodiment.

FIG. 14 is a schematic plan view of a quartz crystal gyro sensor elementof a third embodiment.

FIG. 15 is a perspective view of a gyro sensor of a fourth embodiment.

FIG. 16 is a cross-sectional view of the gyro sensor of the fourthembodiment.

FIG. 17 is a perspective view of the gyro sensor of the fourthembodiment.

FIG. 18 is a schematic plan view of a physical quantity sensor of afifth embodiment.

FIG. 19 is a schematic diagram of a physical quantity detection deviceof a sixth embodiment.

FIG. 20 is a perspective view of the physical quantity detection deviceof the sixth embodiment.

FIG. 21 is another perspective view of the physical quantity detectiondevice of the sixth embodiment.

FIG. 22 is a schematic plan view of a gyro sensor element of a seventhembodiment.

FIG. 23 is a schematic plan view of a physical quantity sensor of aneighth embodiment.

FIG. 24 is a schematic plan view of a physical quantity sensor of aninth embodiment.

FIG. 25 is a schematic plan view of a physical quantity sensor of atenth embodiment.

FIG. 26 is a schematic sectional view of a physical quantity sensor ofthe tenth embodiment.

FIG. 27 is a block diagram illustrating an overall system of a vehiclepositioning device of an eleventh embodiment.

FIG. 28 is a diagram illustrating an action of the vehicle positioningdevice of the eleventh embodiment.

FIG. 29 is a perspective view of an electronic device of a twelfthembodiment.

FIG. 30 is a perspective view of an electronic device of a thirteenthembodiment.

FIG. 31 is a plan view of a portable electronic device of a fourteenthembodiment.

FIG. 32 is a block diagram illustrating a schematic configuration of theportable electronic device of the fourteenth embodiment.

FIG. 33 is a perspective view of a vehicle of a fifteenth embodiment.

FIG. 34 is a block diagram of a system according to a sixteenthembodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the invention will be describedwith reference to the drawings. The invention is not limited by theembodiments described below, and modes to which the invention can beapplied are not limited to the following embodiments. In the descriptionof the drawings, the same reference numerals are given to the sameelements.

First Embodiment

System Configuration

FIG. 1 is a block diagram illustrating a configuration of a positioningsystem 1000 according to a first embodiment. The positioning system 1000is used by being equipped on a vehicle and measures a position of thevehicle. As the vehicle, any vehicle may be used as long as it is movingon the ground which is a substantially horizontal surface such as abicycle, a motorcycle, a four-wheel automobile including a truck and abus, an agricultural machine such as a tractor, a movable constructionmachine such as a bulldozer or a shovel car, and there is no particularlimitation. As illustrated in FIG. 1, the positioning system 1000includes a global positioning system (GPS) module 1002 which is asatellite positioning receiver, an inertial measurement unit (IMU) 100which is an inertia measurement device, and a computation unit 1004.

The GPS module 1002 receives a GPS satellite signal transmitted from aGPS satellite and measures GPS positioning information including a dateand time, a position, a speed, and an attitude represented by latitudeand longitude based on the received GPS satellite signal. A satellitepositioning receiver may be a receiver of a global navigation satellitesystem (GNSS), and may be not a GPS but a satellite positioning receiverusing other satellite positioning systems such as a global navigationsatellite system (GLONASS), GALILEO, a beidou navigation satellitesystem (Beidou) or the like.

The IMU 100 is a sensor unit including an angular velocity sensor 110and an acceleration sensor 120.

The angular velocity sensor 110 is a sensor that measures an angularvelocity in a sensor coordinate system that is a three-dimensionalorthogonal coordinate system associated with the IMU 100, and is alsoreferred to as a gyro sensor.

The angular velocity sensor 110 includes an X-axis angular velocitysensor 112 which detects an angular velocity around the X-axis andoutputs the detected angular velocity as a first angular velocitysignal, a Y-axis angular velocity sensor 114 which detects an angularvelocity around the Y-axis and outputs the detected angular velocity asa second angular velocity signal, and a Z-axis angular velocity sensor116 which detects an angular velocity around the Z-axis and outputs thedetected angular velocity as a third angular velocity signal.

The acceleration sensor 120 measures acceleration in the sensorcoordinate system which is the same as that of the angular velocitysensor 110 and is a three-dimensional orthogonal coordinate systemassociated with the IMU 100. The acceleration sensor 120 includes anX-axis acceleration sensor 122 which detects acceleration in the X-axisdirection and outputs the detected acceleration as a first accelerationsignal, a Y-axis acceleration sensor 124 which detects acceleration inthe Y-axis direction and outputs the detected acceleration as a secondacceleration signal, and a Z-axis acceleration sensor 126 which detectsacceleration in the Z-axis direction and outputs the detectedacceleration as a third acceleration signal.

The computation unit 1004 calculates a position of the positioningsystem 1000 using the GPS module 1002 and measured data of the IMU 100.For example, the inertial navigation computation using the measured dataof the IMU 100 is performed to calculate the position of the positioningsystem 1000. When GPS positioning information is output from the GPSmodule 1002, the position calculated by the inertial navigationcomputation is corrected using the GPS positioning information. Thisbecause although positioning information obtained by the GPS module 1002is higher in accuracy than the position obtained by the inertialnavigation computation using the measured data of the IMU 100, an outputinterval (positioning interval) of the GPS positioning information islonger than an output interval of the measured data of the IMU 100. Forexample, the IMU 100 outputs measured data every 10 milliseconds, andthe GPS module 1002 outputs GPS positioning information every onesecond.

Sensor Coordinate System

The positioning system 1000 is fixedly equipped on the vehicle so that asensor coordinate system which is a three-dimensional orthogonalcoordinate system associated with the IMU 100 satisfies a predeterminedrelationship with respect to a direction of the vehicle. FIG. 2 is adiagram for explaining a relationship between the sensor coordinatesystem and a moving direction of a vehicle 1100. FIG. 2 illustrates anexample in which the positioning system 1000 is equipped on a four-wheelautomobile which is an example of the vehicle 1100. The X-axis of thesensor coordinate system is the front and rear direction of the vehicle1100, and the forward direction (straight advancing direction) is thepositive direction of the X-axis. Further, the Y-axis of the sensorcoordinate system is the left and right direction of the vehicle 1100,and the right direction is the positive direction of the Y-axis. TheZ-axis of the sensor coordinate system is a direction orthogonal to theX-axis and the Y-axis, and the down direction of the vehicle 1100 is thepositive direction of the Z-axis.

In the first embodiment, since the vehicle 1100 moves in a substantiallyhorizontal plane, the XY-plane becomes a moving plane of the vehicle,and a Z-axis positive direction of the Z-axis matches the direction ofgravity. The attitude of the vehicle 1100 is represented by a roll anglearound the X-axis, a pitch angle around the Y-axis, and a yaw anglearound the Z-axis. Further, since the vehicle 1100 moves in asubstantially horizontal plane, the roll angle which is the attitudecorresponds to inclination in the left and right direction of thevehicle 1100, the pitch angle corresponds to inclination in the frontand rear direction of the vehicle 1100, the yaw angle corresponds toconversion or an azimuth in the moving direction of the vehicle 1100.

Angular Velocity Sensor

As the characteristics of the first embodiment, the angular velocitysensor 110 is configured so that a bias error (output error atstationary condition) B and the Allan variance BIS representing biasstability have the following characteristics. That is, the Z-axisangular velocity sensor 116 is configured to have “higher accuracy” thanthe X-axis angular velocity sensor 112 and the Y-axis angular velocitysensor 114.

(A) Bias Error

The X-axis angular velocity sensor 112, the Y-axis angular velocitysensor 114, and the Z-axis angular velocity sensor 116 are configured sothat bias errors of Bx [deg/sec], By [deg/sec], and Bz [deg/sec] satisfythe following expressions (1a) to (1c) when the Bx [deg/sec] is a biaserror of an output signal of the X-axis angular velocity sensor 112, theBy [deg/sec] is a bias error of an output signal of the Y-axis angularvelocity sensor 114, and the Bz [deg/sec] is a bias error of the outputsignal of the Z-axis of the Z-axis angular velocity sensor 116.

P≤(V/Bz)×(1−cos(Bz×T)  (1a)

Bz<Bx  (1b)

Bz<By  (1c)

In the expression (1a), “T” is a positioning interval (second) of theGPS module 1002, and is an interval at which a positioning result isoutput from the GPS module 1002 to the computation unit 1004. “P” is aposition error [m] caused by a bias error B of the output signal of theangular velocity sensor 110 while a vehicle 1100 moves for T seconds atthe moving speed V [m/sec].

FIG. 3 is a diagram for explaining a position error P. FIG. 3 is a viewin which the mobile object 1100 is viewed from above, that is,illustrates a view of the XY-plane in the sensor coordinate system. Theactual movement direction is indicated by the solid line as an originalmovement direction. Since the forward direction of the vehicle 1100 isthe positive direction of the X-axis, the actual moving direction isalso the positive direction of the X-axis. It is assumed that a positionM1 of the vehicle 1100 at the time t₁ is known and set a position of thevehicle 1100 at the time t₂ as “M2”, which is the position calculated bythe inertial navigation computation using the measured data of the IMU100. The distance between the position M2 and the original advancingdirection is the position error P caused by the bias error B of theoutput signal of the angular velocity sensor 110 while the vehicle 1100moves from the time t₁ to the time t₂.

Although the position calculated by the inertial navigation computationbased on the measured data of the IMU 100 deviates from the originalmoving direction, this positional deviation is caused by an error in theattitude based on the measured data of the IMU 100. Specifically, in thefirst embodiment, since the vehicle 1100 moves in a substantiallyhorizontal plane, the positional deviation is caused by an error in theyaw angle which is an attitude.

In the inertial navigation computation, the attitude is calculated byintegrating the angular velocity which is the output signal of theangular velocity sensor 110 with respect to time. That is, a roll anglearound the X-axis calculated by integrating the output signal of theX-axis angular velocity sensor 112 with respect to time, and a pitch(Pitch) angle around the Y-axis is calculated by integrating the outputsignal of the Y-axis angular velocity sensor 114 with respect to time,and the yaw angle around the Z-axis calculated by integrating the outputsignal of the Z-axis angular velocity sensor 116. However, since theoutput signal of the angular velocity sensor 110 includes the bias errorB, the calculated attitude also includes an error. Further, since theoutput signal of the angular velocity sensor 110 is integrated withrespect to time, the error included in the calculated attitude increaseswith the lapse of time.

On the other hand, the attitude can also be calculated from the outputsignal of the acceleration sensor 120. Specifically, the accelerationsensor 120 constantly detects gravitational acceleration G. That is, theX-axis acceleration sensor 122 detects an X-axis direction component ofgravitational acceleration G, the Y-axis acceleration sensor 124 detectsa Y-axis direction component of the gravitational acceleration G, andthe Z-axis acceleration sensor 126 detects a Z-axis direction componentof the gravitational acceleration G. For that reason, by combininggravitational acceleration components of the respective axes based onthe output signals of the respective axes of the acceleration sensor 120at a stationary state, it is possible to calculate the direction of thegravitational acceleration G with respect to the sensor coordinatesystem, that is, the attitude of the vehicle 1100 which is the attitudeof the sensor coordinate system in real space.

Since a bias error is included also in the output signal of theacceleration sensor 120, an error is included also in the attitudecalculated from the output signal of the acceleration sensor 120.However, the error included in the attitude calculated from the outputsignal of the acceleration sensor 120 is not an error which increaseswith the lapse of time but is a stable error with time. Accordingly, bycomplementarily using the attitude calculated from the output signal ofthe acceleration sensor 120, it is possible to calculate the attitudewith stable accuracy with time regardless of the bias error B of theoutput signal of the angular velocity sensor 110.

However, as in the first embodiment, in the case where the vehicle 1100moves on a substantially horizontal plane, the Z-axis of the sensorcoordinate system is substantially coincident with the gravitationalacceleration direction. For that reason, even if the yaw angle of thevehicle 1100 changes, the Z-axis direction component of thegravitational acceleration G hardly changes. Accordingly, with respectto the yaw angle, supplementation by the output signal of theacceleration sensor 120 is almost impossible or extremely difficult.

As illustrated in FIG. 3, in a case where the vehicle 1100 moves on asubstantially horizontal plane, positional deviation calculated by theinertial navigation computation using the measured data of the IMU 100is caused by the error of the yaw angle which is the attitude. Althoughthe yaw angle is calculated from the output signal of the Z-axis angularvelocity sensor 116, as the bias error Bz of the output signal of theZ-axis angular velocity sensor 116 is integrated, the error of the yawangle increases with the lapse of time.

FIG. 4 is a diagram for explaining calculation of the position by theinertial navigation computation. It is assumed that the vehicle 1100linearly moves on a substantially horizontal plane at the moving speed V[m/sec]. Further, the bias error of the Z-axis angular velocity sensor116 is assumed as Bz [deg/sec]. When the position of the vehicle 1100 iscalculated by inertial navigation computation using the measured data ofthe IMU 100 assuming that the position M1 of the vehicle 1100 at thetime t₁ is known, since the error of the yaw angle which is the attitudeincreases with the lapse of time, a trajectory of the position draws alocus gradually moving away from the original moving direction which isthe linear direction.

In the inertial navigation computation, it is repeated to obtain the yawangle from the output signal of the Z-axis angular velocity sensor 116and calculate the position at the next time t assuming that the vehiclehas moved at the moving speed V in the direction of the yaw angle arerepeated, at each predetermined minute time Δt. The error Δθ[deg] of theyaw angle occurring during the minute time Δt[second] is expressed bythe following expression (2).

Δθ=Bz×Δt  (2)

Then, the position error Δp [m] occurring during the minute timeΔt[second] is expressed by the following expression (3).

Δp=V×T×sin Δθ  (3)

By integrating the position error Δp from the time t₁ to the time t₂(=t₁+T) after T seconds with respect to time, the position error P[m]that occurs when moving at the moving speed V[m/sec] during the Tseconds from the time t₁ to the time t₂ is obtained by the followingexpression (4).

P=(V/Bz)λ(1−cos(Bz×T)  (4)

As described above, the position calculated by the inertial navigationcomputation can be corrected by using high accurate GPS positioninginformation output at each positioning interval T from the GPS module1002. For that reason, it is sufficient that the position error Poccurring during the positioning interval T is at least equal to or lessthan the predetermined allowable maximum position error Pp. The extentof the allowable maximum position error Pp is determined depending onthe purpose of use of the vehicle 1100 and the like. Accordingly, theexpression (1a) expressing that the position error P calculated by theexpression (4) becomes equal to or less than the predetermined allowablemaximum position error Pp is a conditional expression to be satisfied bythe bias error Bz of the Z-axis angular velocity sensor 116.

Since the bias error Bx of the X-axis angular velocity sensor 112 andthe bias error By of the Y-axis angular velocity sensor 114 can besupplemented by the output signal of the acceleration sensor 120 asdescribed above, accuracy of the bias errors Bx and By may be lower thanthat of the bias error Bz of the Z-axis angular velocity sensor 116.However, since it is undesirable to have an accuracy as low as to detectthat the vehicle 1100 in the horizontal state has rolled over, the biaserror Bx of the X-axis angular velocity sensor 112 and the bias error Byof the Y-axis angular velocity sensor 114 are conditional on satisfyingthe following expressions (5a) and (5b).

T×Bx<90 [degrees]  (5a)

T×By<90 [degrees]  (5b)

Subsequently, consider specific examples of the bias errors Bx, By, andBz of the angular velocity sensor 110.

Specifically, as a vehicle, assume an agricultural machine that iscontrolled to be automatically operated, a movable construction machine,and a transportation work vehicle. In recent years, in order to realizeautomatic operation control in the agricultural machine, theconstruction machine, and the like, accuracy of centimeter order isrequired for the measurement position of the positioning system 1000equipped on the agricultural machine, the construction machine, and thelike. That is, in a case of automatic operation control of theagricultural machine such as a rice planting machine, the constructionmachine such as a shovel car, the transportation work vehicle such as aforklift truck, and the like, although the moving speed is a low speedof about 15 km/h or less, the accuracy of the position is very importantfrom the purpose of its use. The bias errors Bx, By, and Bz of theangular velocity sensor 110 necessary for responding to this positionalaccuracy requirement are obtained. That is, the error of the yaw anglewhich is the attitude and a position error caused by the error of thisyaw angle were calculated assuming that the moving speed V of thevehicle 1100 is 15 [km/h], which is the general moving speed ofagricultural machine, the construction machine, and the transportationwork vehicle. For calculation, seven types of Z-axis angular velocitysensors 116 having bias errors Bz of 0[deg/hour], 360[deg/hour],570[deg/hour], 760[deg/hour], 890[deg/hour], 1010[deg/hour], and1140[deg/hour], respectively, were assumed.

FIG. 5 is a graph illustrating a relationship between the elapsed timeand an error of the yaw angle which is the attitude, and FIG. 6 is agraph illustrating a relationship between the elapsed time and aposition error. The position error is obtained from the bias error Bzand the moving speed V according to the expression (4). As illustratedin FIG. 5, since the yaw angle is obtained by integrating the outputsignal of the Z-axis angular velocity sensor 116 with respect to time,the error of the yaw angle increases in proportion to the elapsed time.Also, even if the elapsed time is the same, the larger the bias errorBz, the larger the error of the yaw angle. Accordingly, as illustratedin FIG. 6, the position error also increases as the elapsed timeincreases. Even if the elapsed time is the same, as the bias error Bzincreases, the error of the yaw angle increases, so that the positionerror also increases.

Generally, the positioning interval T of the GPS module 1002 is 1[second]. This positioning interval T is a time interval during whichGPS positioning information is not output and corresponds to a period oftime during which position correction based on GPS positioninginformation cannot be performed. In order to allow the position accuracyto satisfy accuracy of centimeter order, it is necessary to set theposition error during the positioning interval T to 10 cm or less.Accordingly, according to FIG. 6, in order to make the elapsed timeequal to or less than 100 mm (=10 cm) at the time point of 1 [second],which is the positioning interval T of the GPS module 1002, the biaserror Bz of the Z-axis angular velocity sensor 116 needs to be570[deg/hour] or less.

There is no problem even if the bias error Bx of the X-axis angularvelocity sensor 112 and the bias error By of the Y-axis angular velocitysensor 114 exceed 1140[deg/hour] greater than the 570[deg/hour]. Thatis, the bias error Bz of the Z-axis angular velocity sensor 116 needs tobe smaller than the bias error Bx of the X-axis angular velocity sensor112 and the bias error By of the Y-axis angular velocity sensor 114.Specifically, the bias error Bz is sufficient to satisfy the followingexpressions (6a) to (6c)).

Bx>1140[deg/hour]  (6a)

By>1140[deg/hour]  (6b)

Bz<570[deg/hour]  (6c)

According to this, it can be said that it is desirable that the biaserror Bz is desirably 50% or less (0.5≈570/1140) of the bias errors Bxand By as illustrated in the following expressions (7a) and (7b).

Bz<0.5×Bx  (7a)

Bz<0.5×By  (7b)

(B) Bias Stability (Allan Variance)

Next, it is assumed that the vehicle equipped with the positioningsystem 1000 is, for example, an agricultural machine or a constructionmachine of which operation is automatically controlled. It is assumedthat the agricultural machine and the construction machine are used inan environment where GPS satellite signals cannot be received due tomultipath and the like by surrounding buildings, forests, and the like.Matters that that accuracy related to long-term stability of therequired measuring position can be secured even in such an environmentwill be described below.

Specifically, the X-axis angular velocity sensor 112, the Y-axis angularvelocity sensor 114, and the Z-axis angular velocity sensor 116 areconfigured so that the Allan variances of BISx[deg/hour],BISy[deg/hour], and BISz[deg/hour] satisfy the following expressions(8a) and (8b) when the BISx [deg/hour] is the Allan variance of anoutput signal of the X-axis angular velocity sensor 112, theBISy[deg/hour] is the Allan variance of an output signal of the Y-axisangular velocity sensor 114, and the BISz[deg/hour] is the Allanvariance of the output signal of the Z-axis of the Z-axis angularvelocity sensor 116.

BISz<0.5×BISx  (8a)

BISz<0.5×BISy  (8b)

Since 1/f noise (fluctuation) that determines bias stability is notmodeled in estimation means of the bias error B such as the Kalmanfilter, that is, the 1/f noise is not eliminated, this causes anincrease in an attitude error due to accumulation of bias errors over along period of time.

FIG. 7 is a graph illustrating an example of an Allan variance curve,and illustrates three types of angular velocity sensors having differentcharacteristics. In general, the Allan variance σ draws a curve in whichit decreases as the time constant (averaging time) τ increases, and thenconverges to a fixed value. This fixed value is taken as the Allanvariance BIS representing bias stability of the first embodiment. In theexample of FIG. 7, the Allan variance BIS is exemplified for three typesof angular velocity sensors with the Allan variance BIS being2.5[deg/hour], 5[deg/hour], and 10[deg/hour].

Subsequently, consider specific examples of Allan variance BISx, BISy,and BISz of the angular velocity sensor 110. Similarly to theconsideration of the specific example of the bias error Bz, assume theagricultural machine, the construction machine, and the transportationwork vehicle of which operations are automatically controlled as thevehicle. Then, the error of the yaw angle which is the attitude and theposition error is calculated assuming that the moving speed V of thevehicle is 15 [km/h], which is a high speed when the agriculturalmachine, the construction machine, and the transportation work vehicleperform a work by automatic operation. For the calculation, three typesof Z-axis angular velocity sensors 116 with the Allan variance BISzbeing 2.5[deg/hour], 5[deg/hour], and 10[deg/hour] were assumed.

FIG. 8 is a graph illustrating a relationship between the elapsed timeand the error of the yaw angle which is the attitude, and FIG. 9 is agraph illustrating a relationship between the elapsed time and theposition error. As illustrated in FIG. 8, the error of the yaw angleincreases as the elapsed time increases. Also, even if the elapsed timeis the same, the larger the Allan variance BISz is, the larger the errorof the yaw angle becomes. Accordingly, as illustrated in FIG. 9, theposition error also increases as the elapsed time increases, and even ifthe elapsed time is the same, the larger the Allan variance BISz is, thelarger the position error becomes.

The position error due to Allan variance becomes a problem in a casewhere the bias error B of the angular velocity sensor 110 is accumulatedover a relatively long period of time. Matters that the assumedagricultural machine and construction machine are used in an environmentin which GPS satellite signals due to multipath or the like bysurrounding buildings, forests or the like cannot be received orreception signals are weak signals, and matters that the worktransportation vehicle is used indoors where it cannot receive the GPSsatellite signal are assumed. Therefore, consider securing a positionerror of approximately 15 [cm] that can be determined as an excessiveerror for automatic operation in a case where a GPS satellite signal isnot received for 30 seconds.

According to FIG. 9, in order to make the position error 15 cm (=150 mm)or less at the time when the elapsed time is 30 seconds, the Allanvariance BISz of the Z-axis angular velocity sensor 116 needs to be2.5[deg/hour]. Then, the Allan variance BISx of the X-axis angularvelocity sensor 112 and the Allan variance BISy of the Y-axis angularvelocity sensor 114 do not cause a problem even if the Allan variancesBISx and BISy are 5[deg/hour] or more which is larger than 2.5[deg/hour]. That is, the Allan variance BISz of the Z-axis angularvelocity sensor 116 needs to be smaller than the Allan variance BISx ofthe X-axis angular velocity sensor 112 and BISy of the Y-axis angularvelocity sensor 114. Specifically, the following expressions (9a) to(9c) may be satisfied.

BISx≥5[deg/hour]  (9a)

BISy≥5[deg/hour]  (9b)

BISz≤2.5[deg/hour]  (9c)

According to this, as illustrated in the expressions (8a) and (8b)described above, it can be said that the Allan variance BISz isdesirably 50% (0.5=2.5/5) or less of the Allan variances BISx and BISy.

Operational Effect

As such, in the first embodiment, the Z-axis angular velocity sensor 116is configured such that the bias error B and the Allan variance BIS aresmaller than those of the X-axis angular velocity sensor 112 and theY-axis angular velocity sensor 114. That is, the Z-axis angular velocitysensor 116 is configured to have “higher accuracy” than the X-axisangular velocity sensor 112 and the Y-axis angular velocity sensor 114.

Specifically, the Z-axis angular velocity sensor 116 has the bias errorBz which is smaller than the bias errors Bx and By of the X-axis angularvelocity sensor 112 and the Y-axis angular velocity sensor 114 and is avalue that makes the position error during the movement of the vehiclemounted with the positioning system 1000 for T[seconds], which is thepositioning interval of the GPS module 1002, equal to or less than thepredetermined allowable maximum position error Pp. With thisconfiguration, the position error due to the positioning system 1000 canbe made to be equal to or less than the allowable maximum position errorPp. The Allan variance BISz of the Z-axis angular velocity sensor 116 issmaller than the Allan variances BISxz and BISy of the X-axis angularvelocity sensor 112 and the Y-axis angular velocity sensor 114. Withthis configuration, even if the GPS satellite signal cannot be receivedfor a predetermined period of time, it is possible to set the positionerror due to the positioning system 1000 within the predeterminedallowable range.

Second Embodiment

Next, a second embodiment will be described. Hereinafter, differencesfrom the first embodiment will be mainly described, and the samereference numerals are given to the same constituent elements as in thefirst embodiment, and redundant description thereof will be omitted. Thesecond embodiment is an embodiment of a sensor unit that is the IMU 100in the first embodiment.

Outline of Sensor Unit

FIG. 10 is a perspective view for explaining a state of fixing a sensorunit 160 to a mounted surface 19 according to a second embodiment. FIG.11 is a perspective view of the sensor unit 160 when viewed from themounted surface 19 side of FIG. 10. First, an outline of the sensor unit160 according to the second embodiment will be described.

In FIGS. 10 and 11, the sensor unit 160 is an inertial measurement unit(IMU) which is an inertia measurement device and detects the attitudeand behavior (inertial momentum) of a moving body (mounted device) suchas a car or a moving body such as a robot. The sensor unit 160 includesa plurality of inertial sensors, for example, a triaxial accelerationsensor 120 which measures acceleration acting in directions of threeaxes orthogonal to each other and a three-axis angular velocity sensor110 which measures an angular velocity acting around each axis.

The sensor unit 160 is a rectangular parallelepiped having a planarshape of a rectangle, and includes screw holes 2 as fixing portionsformed in the vicinity of two apexes positioned in the diagonaldirection of the rectangle. The sensor unit 160 is used in a state ofbeing fixed on the mounted surface 19 of a mounted object (device) suchas an automobile through two screws 5 in the two screw holes 2. Theshape described above is an example, and it is possible to reduce thesize of the sensor unit to a size that can be mounted on, for example,various wearable electronic devices, smart phones, digital cameras, andthe like by selection of parts and design change.

As illustrated in FIG. 11, an opening 4 is formed on the surface of thesensor unit 160 when viewed from the mounted surface side. A plug type(male) connector 10 is disposed inside (inside) the opening 4. In theconnector 10, a plurality of pins are arranged side by side. A connector(not illustrated) of a socket type (female) is connected to theconnector 10 from the mounted device, and transmission and reception ofelectrical signals such as power supply to the sensor unit 160 andoutput of detection data detected by the sensor unit 160 are performedbetween the sensor unit 160 and the mounted device.

Configuration of Sensor Unit

FIG. 12 is an exploded perspective view of the sensor unit 160 whenviewed in the same direction as FIG. 11. Subsequently, a configurationof the sensor unit 160 will be described in detail with reference mainlyto FIG. 12 while appropriately combining FIG. 10 and FIG. 11. Asillustrated in FIG. 12, the sensor unit 160 is configured with an outercase 1, an annular cushioning material 6, a sensor module 7, and thelike. In other words, a configuration in which the sensor module 7 ismounted on the inside 3 of the outer case 1 with an annular cushioningmaterial 6 interposed therebetween is adopted. The sensor module 7 isconfigured with an inner case 8 and a circuit board 9. In order to makethe description easier to understand, although the outer case and theinner case are used as the part names, the outer case and the inner casemay be referred to as a first case and a second case.

The outer case 1 is a pedestal from which aluminum is cut out into a boxshape. The material thereof is not limited to aluminum, but other metalssuch as zinc and stainless steel, a resin, a composite material of ametal and a resin, or the like may be used. The outer shape of the outercase 1 is a rectangular parallelepiped having a planar shape of arectangle similarly to the overall shape of the sensor unit 160described above, and the screw holes 2 are respectively formed in thevicinity of two apexes positioned in the diagonal direction of thesquare. An example in which the outer shape of the outer case 1 is arectangular parallelepiped having a planar shape of a rectangle and abox shape without a lid is described, but is not limited thereto. Theplanar shape of the outer shape of the outer case 1 may be a polygonsuch as a hexagon or an octagon, and corners of the apex portion of thepolygon may be chamfered, each side may be curved, or the outer shapemay be circular.

Configuration of Circuit Board

FIG. 13 is a perspective view of the circuit board 9. The configurationof the circuit board 9 on which a plurality of inertial sensors aremounted will be described below. The circuit board 9 is a multilayersubstrate having a plurality of through-holes formed therein, and aglass epoxy substrate is used. The invention is not limited to the glassepoxy substrate, but may be a rigid substrate capable of mounting aplurality of inertial sensors, electronic components, connectors and thelike. For example, a composite substrate or a ceramic substrate may beused. On the surface of the circuit board 9 (surface on the side of theinner case 8), a connector 10, a multi-axis inertial sensor 17 in whichthree-axis angular velocity sensors and three-axis acceleration sensorsare accommodated, and a high-accuracy angular velocity sensor 18, andthe like are installed. The connector 10 is a plug type (male)connector, and includes two rows of connection terminals in which aplurality of pins are disposed at an equal pitch. The number ofterminals may be appropriately changed according to designspecifications.

The high-accuracy angular velocity sensor 18 is a gyro sensor fordetecting an angular velocity of one axis in the Z-axis direction whichis the direction of gravity. In the vehicle on which the sensor unit 160is mounted, when a preset straight advancing direction of the vehicle isset as an X-axis, a gravitational direction of the vehicle is set as aZ-axis, and an axis orthogonal to the X-axis and the Z-axis set as aY-axis, the sensor unit 160 functions as a Z-axis angular velocitysensor which detects an angular velocity around the Z-axis and outputsan angular velocity signal around the Z-axis, and calculates the yaw(YAW) angle around the Z-axis of the vehicle based on the angularvelocity signal around the Z-axis.

As a preferable example of the high-accuracy angular velocity sensor 18,a resonance frequency change type crystal gyro sensor in which quartzcrystal is used as a material and which measures an angular velocityfrom a Coriolis force applied to a vibrating object is used. Further,the high-accuracy angular velocity sensor 18 is not limited to thequartz crystal-crystal gyro sensor, but may be a multi-gyro sensor inwhich a plurality of electrostatic capacitance change type silicon-microelectro mechanical systems (Si-MEMS) angular velocity sensors areconnected in a multi-connected manner.

The multi-axial inertial sensor 17 includes an X-axis angular velocitysensor 112 which detects an angular velocity around the X-axis andoutputs a first angular velocity signal, a Y-axis angular velocitysensor 114 which detects an angular velocity around the Y-axis andoutputs a second angular velocity signal, a Z-axis angular velocitysensor 116 which detects an angular velocity around the Z-axis andoutputs a third angular velocity signal, an X-axis acceleration sensor122 which detects acceleration in the X-axis direction and outputs afirst acceleration signal, a Y-axis acceleration sensor 124 whichdetects acceleration in the Y-axis direction and outputs a secondacceleration signal, and a Z-axis acceleration sensor 126 which detectsacceleration in the Z-axis direction, and outputs a third accelerationsignal. Here, since the high-accuracy angular velocity sensor 18installed on the circuit board 9 by itself functions as the Z-axisangular velocity sensor 116 which detects the angular velocity aroundthe Z-axis and outputs the angular velocity signal around the Z-axis,the Z-axis angular velocity sensor is not necessarily mounted, for themulti-axis inertial sensor 17. In the case where the Z-axis angularvelocity sensor is mounted on the multi-axis inertial sensor 17, thehigh-accuracy angular velocity sensor 18 and the Z-axis angular velocitysensor may share the functional role as appropriate according to designspecifications and the like.

As the acceleration sensor 120 mounted on the multi-axis inertial sensor17, an electrostatic capacitance change type Si-MEMS acceleration sensor(acceleration sensor) capable of measuring (detecting) acceleration inthe X-axis direction, the Y-axis direction, and the Z-axis directionwith one device (one chip) is used. That is, the acceleration sensor 120mounted on the multi-axis inertial sensor 17 includes the X-axisacceleration sensor 122 which detects acceleration in the X-axisdirection and outputs the first acceleration signal, and the Y-axisacceleration sensor 124 which detects acceleration in the Y-axisdirection and outputs the second acceleration signal, and the Z-axisacceleration sensor 126 which detects acceleration in the Z-axisdirection and outputs the third acceleration signal.

The acceleration sensor 120 is not limited to this capacitance changetype Si-MEMS acceleration sensor, and it suffices if the accelerationsensor 120 is a sensor capable of detecting acceleration. For example,the acceleration sensor 120 may be a frequency change type quartzcrystal acceleration sensor, a piezo-resistive type acceleration sensor,or a heat detection type acceleration sensor, or the acceleration sensor120 may have a configuration in which one acceleration sensor isprovided for each axis like the high-accuracy angular velocity sensor 18described above.

A control IC 11 is mounted on the back surface (surface on the outercase 1 side) of the circuit board 9.

The control IC 11 is a micro controller unit (MCU), and incorporates astoring unit including a nonvolatile memory, an A/D converter, and thelike and controls each unit of the sensor unit 160. In the storing unit,a program defining the sequence and contents for detecting accelerationand angular velocity, a program for digitizing detected data to beincorporated into packet data, accompanying data, and the like arestored. On the circuit board 9, a plurality of other electroniccomponents are mounted.

Third Embodiment

Next, a third embodiment will be described. Hereinafter, differencesfrom the first and second embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose in the first and second embodiments, and redundant descriptionwill be omitted. The third embodiment is an embodiment of a quartzcrystal gyro sensor element which is the high-accuracy angular velocitysensor 18 in the second embodiment.

Configuration of High Accuracy Angular Velocity Sensor

In the high-accuracy angular velocity sensor 18 of the third embodiment,by adopting quartz crystal (SiO₂) as the material, a high Q value isobtained from high crystallinity of the quartz crystal andcharacteristics in which impedance characteristic and frequencytemperature characteristic are stable over a wide temperature range canbe exhibited. In general, the Q value of the quartz crystal isapproximately 30,000, whereas the Q value of the Si-MEMS constitutingthe capacitance type angular velocity sensor element is approximately5,000, which is extremely low and is one-sixth of the Q value of quartz.Since the Q value of quartz crystal is much higher than the Q value ofSi-MEMS, in the high-accuracy angular velocity sensor 18 made of quartzcrystal, vibration characteristics in which the amplitude is large evenat a drive voltage lower than the drive voltage of Si-MEMS and noise issmall are obtained and thus, excellent characteristics having a largeS/N ratio compared with that of the Si-MEMS are obtained.

FIG. 14 is a schematic plan view illustrating a quartz crystal gyrosensor element 200 of the third embodiment.

The quartz crystal gyro sensor element 200 is formed using quartzcrystal, which is a piezoelectric material, as a base material. Thequartz crystal has an X-axis called an electric axis, a Y-axis called amechanical axis, and a Z-axis called an optical axis. The quartz crystalgyro sensor element 200 is cut along a plane defined by the X-axis andY-axis orthogonal to the quartz crystal axis and processed into a flatplate shape, and has a predetermined thickness in the Z-axis directionorthogonal to the plane. The predetermined thickness is appropriatelyset depending on an oscillation frequency (resonance frequency),external size, workability, and the like.

It should be noted that the X-axis, the Y-axis, and the Z-axis describedin the third embodiment indicate the electric axis, the mechanical axis,and the optical axis which are crystal axes of quartz crystal, and havedifferent meanings from the X-axis, the Y-axis, and the Z-axis in thesensor coordinate system which is a three-dimensional orthogonalcoordinate system associated with the IMU 100 described in the firstembodiment.

Further, the flat plate constituting the quartz crystal gyro sensorelement 200 can allow an error of a cutting angle from the quartzcrystal to some extent for each of the X-axis, the Y-axis, and theZ-axis. For example, it is possible to use the flat plate which isrotated in a range of 0 degrees to 2 degrees around the X-axis and cutout. This also applies to the Y-axis and the Z-axis. The crystal gyrosensor element 200 is formed by etching (wet etching or dry etching)using the photolithography technique. A plurality of crystal gyro sensorelements 200 can be taken out from one quartz crystal wafer.

As illustrated in FIG. 14, the quartz crystal gyro sensor element 200has a so-called double T type configuration. The quartz crystal gyrosensor element 200 includes a base portion 210 positioned at the centerportion and a pair of detection vibration arms 211 a and 211 b one ofwhich extending linearly along the Y-axis from the base portion 210 inthe plus direction of the Y-axis and the other of which extendinglinearly along the Y-axis from the base portion 210 in the minusdirection of the Y-axis. Further, the quartz crystal gyro sensor element200 includes a pair of connection arms 213 a and 213 b one of whichextends linearly along the X-axis from the base portion 210 in the plusdirection of the X-axis and the other of which extends linearly alongthe X-axis from the base portion 210 in the minus direction of theX-axis so as to be orthogonal to the detection vibration arms 211 a and211 b. Further, the quartz crystal gyro sensor element 200 includes apair of drive vibration arms 214 a and 214 b and a pair of drivevibration arms 215 a and 215 b, and in the pair of drive vibration arms214 a and 214 b, one of the drive vibration arms extends linearly alongthe Y-axis from the tip end side of a connection arms 213 a in the plusdirection of the Y-axis and the other of the drive vibration armsextends linearly along the Y-axis from the tip end side of theconnection arms 213 a in the minus direction of the Y-axis so as to beparallel to the detection vibration arm 211 a, and in the pair of drivevibration arms 215 a and 215 b, one of the drive vibration arms extendslinearly along the Y-axis from the tip end side of a connection arm 213b in the plus direction of the Y-axis and the other of the drivevibration arms extends linearly along the Y-axis from the tip end sideof the connection arm 213 b in the minus direction of the Y-axis so asto be parallel to the detection vibration arm 211 b.

In the crystal gyro sensor element 200, detection electrodes (notillustrated) are formed on the detection vibration arms 211 a and 211 band drive electrodes (not illustrated) are formed on drive vibrationarms 214 a, 214 b, 215 a, and 215 b. In the quartz crystal gyro sensorelement 200, a detecting vibration system for detecting the angularvelocity is configured with the detection vibration arms 211 a and 211 band a drive vibration system for driving the quartz crystal gyro sensorelement 200 is configured with the connection arms 213 a and 213 b andthe drive vibration arms 214 a, 214 b, 215 a, and 215 b.

In addition, weight portions 212 a and 212 b are formed at the tip endportions of the detection vibration arms 211 a and 211 b, respectively,and weight portions 216 a, 216 b, 217 a, and 217 b are formed at the tipend portions of the drive vibration arms 214 a, 214 b, 215 a, and 215 b,respectively. With this configuration, the quartz crystal gyro sensorelement 200 is reduced in size and improved in detection sensitivity ofangular velocity. The detection vibration arms 211 a and 211 b includethe weight portions 212 a and 212 b, and the drive vibration arms 214 a,214 b, 215 a, 215 b include weight portions 216 a, 216 b, 217 a, and 217b.

Furthermore, in the crystal gyro sensor element 200, four beams 220 a,220 b, 221 a, and 221 b extend from the base portion 210. The beam 220 aextends from the outer edge of the base portion 210 between theconnection arm 213 a and the detection vibration arm 211 a. The beam 220b as a first beam extends from the outer edge of the base portion 210between the connection arm 213 b positioned on the plus side from thebase portion 210 in the X-axis direction and the detection vibration arm211 a positioned on the plus side from the base portion 210 in theY-axis direction. The beam 221 a extends from the outer edge of the baseportion 210 between the connection arm 213 a and the detection vibrationarm 211 b. The beam 221 b as a second beam extends from the outer edgeof the base portion 210 between the connection arm 213 b positioned onthe plus side from the base portion 210 in the X-axis direction and thedetection vibration arm 211 b positioned on the plus side from the baseportion 210 in the Y-axis direction.

The beam 220 b is configured to include a first folded portion 220 cincluding a first extending portion 220 b 1 extending from the baseportion 210 along the X-axis in the plus direction of the X-axis, asecond extending portion 220 b 2 extending from the tip end portion ofthe first extending portion 220 b 1 along the Y-axis in the plusdirection of the Y-axis, and a third extending portion 220 b 3 extendingfrom the tip end portion of the second extending portion 220 b 2 alongthe X-axis in the minus direction of the X-axis.

The beam 221 b is configured to include a second folded portion 221 cincluding a fourth extending portion 221 b 1 extending from the baseportion 210 along the X-axis in the plus direction of the X-axis, afifth extending portion 221 b 2 extending from the tip end portion ofthe fourth extending portion 221 b 1 along the Y-axis in the minusdirection of the Y-axis, and a sixth extending portion 221 b 3 extendingfrom the tip end portion of the fifth extending portion 221 b 2 alongthe X-axis in the minus direction of the X-axis.

Each of the beams 220 a, 220 b, 221 a, and 221 b of the crystal gyrosensor element 200 is rotationally symmetric with respect to the centerof gravity G of the quartz crystal gyro sensor element 200.Specifically, the beam 220 a and the beam 221 b are in a rotationallysymmetrical shape with the center of gravity G of the quartz crystalgyro sensor element 200 as the rotation center, and the beam 221 a andthe beam 220 b are in a rotationally symmetrical shape around the centerof gravity G of the quartz crystal gyro sensor element 200. With thisconfiguration, a folded portion 220 d which is in a rotationallysymmetric shape with respect to the second folded portion 221 c isformed in the beam 220 a, and a folded portion 221 d which is in arotationally symmetric shape with respect to the first folded portion220 c is formed in the beam 221 a.

The tip end portions of the beams 220 a and 220 b are connected to asupport portion 222 positioned on the plus side from the detectionvibration arm 211 a in the Y-axis direction and extending along theX-axis, and the tip end portions of the beams 221 a and 221 b areconnected to a support portion 223 positioned on the minus side from thedetection vibration arm 211 b in the Y-axis direction and extendingalong the X-axis. It is preferable from the viewpoint of balance thatthe support portion 222 and the support portion 223 are in arotationally symmetrical shape with the center of gravity G of thequartz crystal gyro sensor element 200 as the rotation center. Thequartz crystal gyro sensor element 200 is supported by the supportportions 222 and 223 being fixed to a support table or the like whichwill be described later.

Fourth Embodiment

Next, a fourth embodiment will be described. Hereinafter, differencesfrom the first to third embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose in the first to third embodiments, and redundant descriptionthereof will be omitted. The fourth embodiment is an embodiment of aphysical quantity sensor which is the high-accuracy angular velocitysensor 18 in the second embodiment.

A gyro sensor (physical quantity sensor) 300 as an example of theelectronic device illustrated in FIGS. 15, 16, and 17 includes a quartzcrystal gyro sensor element 32 as a function element for detecting theangular velocity, a first support base material 39 a and a secondsupport base material 39 b constituting a support portion for supportingthe quartz crystal gyro sensor element 32, and a package 35 forcollectively accommodating support portions divided into the quartzcrystal gyro sensor element 32, the first support base material 39 a,and the second support base material 39 b. The quartz crystal gyrosensor element 32 is, for example, the quartz crystal gyro sensorelement 200 in the third embodiment. The package 35 includes a base 36and a lid 37 joined to the base 36.

Fifth Embodiment

Next, a fifth embodiment will be described. Hereinafter, differencesfrom the first to fourth embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose of the first to fourth embodiments, and redundant descriptionthereof will be omitted. The fifth embodiment is an embodiment of aphysical quantity sensor which is the high-accuracy angular velocitysensor 18 in the second embodiment.

A physical quantity sensor 400 illustrated in FIG. 18 is a Si-MEMS typeangular velocity sensor element capable of measuring an angular velocityωz around the Z-axis.

As illustrated in FIG. 18, a shape of an element portion 404 issymmetrical with respect to an imaginary straight line α. The elementportion 404 includes drive portions 41A and 41B disposed on both sidesof the imaginary straight line α. The drive portion 41A includes atooth-shaped movable drive electrode 411A and a fixed drive electrode412A which is formed in a tooth shape and disposed to be in mesh withthe movable drive electrode 411A. Similarly, the drive portion 41Bincludes a tooth-shaped movable drive electrode 411B and a fixed driveelectrode 412B which is formed in a tooth shape and disposed to be inmesh with the movable drive electrode 411B.

The fixed drive electrode 412A is positioned outside (farther from theimaginary straight line α) than the movable drive electrode 411A, andthe fixed drive electrode 412B is positioned outside (side farther fromthe imaginary straight line α) than the movable drive electrode 411B.Each of the fixed drive electrodes 412A and 412B is joined to the uppersurface of a mount 221 and is fixed to the substrate 402. Each of themovable drive electrodes 411A and 411B is electrically connected to awiring 73 and each of the fixed drive electrodes 412A and 412B iselectrically connected to a wiring 74.

In addition, the element portion 404 includes four fixed portions 42Adisposed around the drive portion 41A and four fixed portions 42Bdisposed around the drive portion 41B. Each of the fixing portions 42Aand 42B is joined to the upper surface of the mount and is fixed to thesubstrate 402.

The element portion 404 includes four drive springs 43A connecting thefixed portions 42A and the movable drive electrode 411A and four drivesprings 43B connecting the fixed portions 42B and the movable driveelectrode 411B. The drive springs 43A are elastically deformed in theX-axis direction so that displacement of the movable drive electrode411A in the X-axis direction is permitted and the driving springs 43Bare elastically deformed in the X-axis direction so that displacement ofthe movable drive electrode 411B in the X-axis direction is permitted.

When a drive voltage is applied between the movable drive electrodes411A and 411B and the fixed drive electrodes 412A and 412B through thewirings 73 and 74, electrostatic attractive forces are generated betweenthe movable drive electrode 411A and the fixed drive electrode 412A andbetween the movable drive electrode 411B and the fixed drive electrode412B, and the movable drive electrode 411A vibrates in the X-axisdirection while elastically deforming the drive spring 43A in the X-axisdirection and the movable drive electrode 411B vibrates in the X-axisdirection while elastically deforming the drive spring 43B in the X-axisdirection. Since the drive portions 41A and 41B are disposedsymmetrically with respect to the imaginary straight line α, the movabledrive electrodes 411A and 411B vibrate in opposite phases in the X-axisdirection so as to repeat approaching and separating from each other.For that reason, vibration of the movable drive electrodes 411A and 411Bis canceled, and vibration leakage can be reduced. Hereinafter, thisvibration mode is also referred to as a drive vibration mode.

In the physical quantity sensor 400 of the fifth embodiment, although anelectrostatic drive method is used in which the drive vibration mode isexcited by electrostatic attractive force is applied, a method ofexciting the drive vibration mode is not particularly limited, and forexample, a piezoelectric drive method, an electromagnetic drive methodusing a Lorentz force of a magnetic field, or the like can also beapplied.

Further, the element portion 404 includes detection portions 44A and 44Bdisposed between the drive portions 41A and 41B. The detection portion44A includes a movable detection electrode 441A having a plurality ofelectrode fingers disposed in a tooth shape and fixed detectionelectrodes 442A and 443A disposed to be in mesh with electrode fingersof the movable detection electrode 441A provided with a plurality ofelectrode fingers disposed in a tooth shape. The fixed detectionelectrodes 442A and 443A are arranged side by side in the Y-axisdirection, and the fixed detection electrode 442A is positioned on theplus side in the Y-axis direction and the fixed detection electrode 443Ais positioned on the minus side in the Y-axis direction with respect tothe center of the movable detection electrode 441A. In addition, a pairof the fixed detection electrodes 442A and a pair of fixed detectionelectrodes 443A are arranged so as to sandwich the movable detectionelectrode 441A from both sides in the X-axis direction.

The movable detection electrode 441A has mass different from that of themovable drive electrode 411A. In the fifth embodiment, the mass of themovable detection electrode 441A is larger than the mass of the movabledrive electrode 411A. However, the mass of the movable detectionelectrode 441A is not limited thereto, and the mass of the movabledetection electrode 441A may be equal to the mass of the movable driveelectrode 411A, or may be smaller than the mass of the movable driveelectrode 411A.

Similarly, the detection portion 44B includes a movable detectionelectrode 441B having a plurality of electrode fingers disposed in atooth shape and fixed detection electrodes 442B and 443B disposed to bein mesh with electrode fingers of the movable detection electrode 441Bprovided with a plurality of electrode fingers disposed in a toothshape. The fixed detection electrodes 442A and 443B are arranged side byside in the Y-axis direction, and the fixed detection electrode 442B ispositioned on the plus side in the Y-axis direction and the fixeddetection electrode 443B is positioned on the minus side in the Y-axisdirection with respect to the center of the movable detection electrode441B. In addition, a pair of the fixed detection electrodes 442B and apair of fixed detection electrodes 443B are arranged so as to sandwichthe movable detection electrode 441B from both sides in the X-axisdirection.

The movable detection electrode 441B has mass different from that of themovable drive electrode 411B. In the fifth embodiment, the mass of themovable detection electrode 441B is larger than the mass of the movabledrive electrode 411B. However, the mass of the movable detectionelectrode 441B is not limited thereto, and the mass of the movabledetection electrode 441B may be equal to the mass of the movable driveelectrode 411B, or may be smaller than the mass of the movable driveelectrode 411B.

The movable detection electrodes 441A and 441B are electricallyconnected to the wiring 73, respectively, the fixed detection electrodes442A and 443B are electrically connected to the wiring 75, respectively,and the fixed detection electrodes 443A and 442B are electricallyconnected to the wiring 76, respectively. When the physical quantitysensor 400 is driven, an electrostatic capacitance Ca is formed betweenthe movable detection electrode 441A and the fixed detection electrode442A and between the movable detection electrode 441B and the fixeddetection electrode 443B, and an electrostatic capacitance Cb is formedbetween the movable detection electrode 441A and the fixed detectionelectrode 443A and between the movable detection electrode 441B and thefixed detection electrode 442B.

Further, the element portion 404 includes two fixed portions 451 and 452disposed between the detection portions 44A and 44B. The fixed portions451 and 452 are respectively bonded to the upper surface of the mountand fixed to the substrate 402. The fixed portions 451 and 452 arearranged in the Y-axis direction and spaced apart from each other. Inthe fifth embodiment, the movable drive electrodes 411A and 411B and themovable detecting electrodes 441A and 441B are electrically connected tothe wiring 73 via the fixed portions 451 and 452.

In addition, the element portion 404 includes four detection springs 46Afor connecting the movable detection electrode 441A and the fixedportions 42A, 451, and 452, and four detection springs 46B forconnecting the movable detection electrode 441B and the fixed portions42B, 451, and 452. The detection springs 46A are elastically deformed inthe X-axis direction so that displacement of the movable drive electrode441A in the X-axis direction is permitted and the detection springs 46Aare elastically deformed in the Y-axis direction so that displacement ofthe movable drive electrode 441A in the Y-axis direction is permitted.Similarly, the detection springs 46B are elastically deformed in theX-axis direction so that displacement of the movable drive electrode441B in the X-axis direction is permitted, and the detection springs 46Bare elastically deformed in the Y-axis direction so that displacement ofthe movable drive electrode 441B in the Y-axis direction is permitted.

Further, the element portion 404 includes a reverse phase spring 47Adisposed between the drive portion 41A and the detection portion 44A andconnecting the movable drive electrode 411A and the movable detectingelectrode 441A and a reverse phase spring 47B disposed between the driveportion 41B and the detection portion 44B and connecting the movabledrive electrode 411B and the movable detecting electrode 441B. Thereverse phase spring 47A is elastically deformed in the X-axis directionso that the movable detection electrode 441A can be displaced in theX-axis direction with respect to the movable drive electrode 411A.Similarly, the reverse phase spring 47B is elastically deformed in theX-axis direction so that the movable detection electrode 441B can bedisplaced in the X-axis direction with respect to the movable driveelectrode 411B.

When the Si-MEMS type angular velocity sensor element is driven with adrive voltage (for example, 1.8 V) equivalent to that of the quartzcrystal gyro sensor element, stable vibration characteristics cannot beobtained, so that it is necessary to further generate a bias voltage(for example, 15 V) of ten and several V using a bias generation circuitfor a drive voltage (for example, 1.8 V) and drive the Si-MEMS typeangular velocity sensor element. However, since noise generated by thebias generation circuit is increased, a signal to noise ratio (S/Nratio) cannot be increased, and it is difficult to obtain low noiseelectrical characteristics as in the quartz gyro sensor element.

Sixth Embodiment

Next, a sixth embodiment will be described. Hereinafter, differencesfrom the first to fifth embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose of the first to fourth embodiments, and redundant descriptionthereof will be omitted. The sixth embodiment is an embodiment of aphysical quantity detection device which is the high-accuracy angularvelocity sensor 18 in the second embodiment.

In a physical quantity detection device 300 of the sixth embodiment, aplurality of physical quantity detection elements 302 are connected in amulti-connected manner. A physical quantity detection element 302 is,for example, the physical quantity sensor 400 in the fifth embodiment.

In the physical quantity detection device 300 configured as describedabove, since a plurality of physical quantity detection elements 302 areelectrically connected to terminals XP and XN of a physical quantitydetection circuit through terminals 307 (for output signals) andterminals 308 (ground (GND) terminals), when it is assumed that thenumber of the physical quantity detection elements 302 is M and physicalquantity components included in signals output from M physical quantitydetection elements 302 are s1_(X), s2_(X), . . . , sM_(X), respectively,the physical quantity component S_(X) included in the signals input fromthe terminals XP and XN is expressed by the following expression (10).

S _(X) =s1_(X) +s2_(X) + . . . +sM _(X)  (10)

Structures of the M physical quantity detection elements 302 are thesame, and when it is assumed that s1_(X)≈s2_(X)= . . . ==SM_(X)=s_(X) inthe expression (10), the expression (10) is transformed as illustratedin the following expression (11).

S _(X) =M·s _(X)  (11)

On the other hand, there is no correlation between white noisecomponents simultaneously output from the M physical quantity detectionelements 302 through the terminals 307 and 308 of the physical quantitydetection circuit. Accordingly, when it is assumed that the white noisecomponents included in the signals output from the M physical quantitydetection elements 302 are n1_(X), n2_(X), . . . , nM_(X), a white noisecomponent N_(X) included in the signals input from the terminals XP andXN of the physical quantity detection is represented by the followingexpression (12).

N _(X)=√{square root over ((n1_(X))²+(n2_(X))²+ . . . +(nM_(X))²)}  (12)

Structures of the M physical quantity detection elements 302 are thesame, and when it is assumed that (n1_(X))²≈(n2_(X))²= . . .=(nM_(X))²=(n_(X))² in the expression (12), the expression (12) istransformed as illustrated in the following expression (13).

N _(X)=√{square root over (M)}·n _(X)  (13)

By dividing the expression (11) by the expression (13), the followingexpression (14) is obtained.

$\begin{matrix}{\frac{S_{X}}{N_{X}} = {\sqrt{M} \cdot \frac{S_{X}}{n_{X}}}} & (14)\end{matrix}$

In the expression (14), the signal to noise ratio of the signal inputfrom the terminals XP and XN of the physical quantity detection circuitis √M times (for example, twice if M=4) the S/N ratio of the outputsignal of each of the M physical quantity detection elements 302.Accordingly, according to the physical quantity detection device 300 ofthe sixth embodiment, the S/N ratio of the output angular velocitysignal is improved.

According to a mounting form illustrated in FIG. 19, since the pluralityof physical quantity detection elements 302 are mounted on a commonsubstrate 360, the distance between the adjacent physical quantitydetection elements 302 can be reduced. Also, since wirings 361, 362, and363 are provided on the substrate 360, the distance between eachphysical quantity detection element 302 and the wirings 361, 362, and363 is reduced, which is advantageous for miniaturizing the physicalquantity detection device 300.

According to the mounting form illustrated in FIG. 20 and the mountingform illustrated in FIG. 21, since the plurality of containers 310 onwhich the plurality of physical quantity detection elements 302 aremounted are stacked, a disposition area of the plurality of physicalquantity detection elements 302 becomes small, and the physical quantitydetection device 300 can be miniaturized. Furthermore, according to themounting form illustrated in FIG. 20 and the mounting form illustratedin FIG. 21, there is no need to provide wirings for electricallyconnecting the terminals 307 and 308 to the terminals XP and XN on adedicated wiring substrate, which is advantageous for miniaturizing thephysical quantity detection device 300.

Accordingly, the high-accuracy angular velocity sensor 18 according tothe sixth embodiment is configured by connecting the plurality ofphysical quantity detection elements 302 as a plurality of Si-MEMS typeangular velocity sensor elements as described above, thereby making itpossible to improve the S/N ratio of the angular velocity signal outputfrom the high-accuracy angular velocity sensor 18.

In the sixth embodiment, although the high-accuracy angular velocitysensor 18 which is the Z-axis angular velocity sensor 116 is described,similarly, the X-axis angular velocity sensor 112 and the Y-axis angularvelocity sensor 114 can be configured as the physical quantity detectiondevice 300 in which the physical quantity detection elements 302 whichare a plurality of sensor elements are connected in a multi-connectedmanner. In this case, the sensor element may be, for example, a gyrosensor element in the seventh embodiment which will be described later.

By setting the number Ngz of the sensor elements constituting the Z-axisangular velocity sensor 116 to be larger than the number Ngx of thesensor elements constituting the X-axis angular velocity sensor 112 andthe number Ngy of the sensor elements constituting the Y-axis angularvelocity sensor 114, the Z-axis angular velocity sensor 116 can be made“high accuracy” as compared with the X-axis angular velocity sensor 112and the Y-axis angular velocity sensor 114. For example, it ispreferable to set the number Ngz of the sensor elements constituting theZ-axis angular velocity sensor 116 to a value larger than 2 elements,that is, 3 or more sensor elements. As the number of sensor elementsincreases, statistical computation and numerical analysis such asutilizing an average value and median value becomes possible, resultingin “high accuracy”.

Seventh Embodiment

Next, a seventh embodiment will be described. Hereinafter, differencesfrom the first to sixth embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose in the first to sixth embodiments, and redundant descriptionthereof will be omitted. The seventh embodiment is an embodiment of gyrosensor elements mounted on the multi-axis inertial sensor 17 in thesecond embodiment, which are the X-axis angular velocity sensor 112 andthe Y-axis angular velocity sensor 114 in the first embodiment.

A gyro sensor element 500 illustrated in FIG. 22 is an angular velocitysensor capable of detecting an angular velocity around the X-axis. Thegyro sensor element 500 illustrated in FIG. 22 has two structures 50 (50a and 50 b) and two fixed detection portions 59 (59 a and 59 b) alignedin the Y-axis direction. The two structures 50 a and 50 b are configuredsymmetrically in the vertical direction toward FIG. 22, and haveconfigurations similar to each other.

Each structure 50 includes a mass portion 51, a plurality of fixedportions 52, a plurality of elastic portions 53, a plurality of driveportions 54 (movable drive electrodes), a plurality of fixed driveportions 55 and 56 (fixed drive electrodes), detection portions 571 and572 (movable detection electrodes), and a plurality of beams 58. Themass portion 51 is integrally formed including the drive portions 54, aframe 573, the detection portions 571 and 572, and the beams 58. Thatis, the detection portions 571 and 572 are in a shape included in themass portion 51.

The outer shape of the mass portion 51 is a quadrilateral frame shape ina plan view when seen in the Z-axis direction (hereinafter, simplyreferred to as “a plan view”), and includes the drive portion 54, theframe 573, the detection portions 571 and 572 as described above.Specifically, the outer shape of the mass portion 51 is configured witha pair of portions extending in parallel to each other in the Y-axisdirection and a pair of portions connecting end portions of the pair ofportions and extending parallel to each other along the X-axisdirection.

Four fixed portions 52 are provided for one structure 50, and each fixedportion 52 is fixed to the substrate. In addition, each of the fixingportions 52 is disposed outside the mass portion 51 in a plan view, andin the seventh embodiment, each of the fixing portions 52 is disposed ata position corresponding to each corner portion of the mass portion 51.In the illustration, the fixed portion 52 positioned on the −Y-axis sideof the structure 50 a and the fixed portion 52 positioned on the +Y-axisside of the structure 50 b are used as a common fixed portion.

Four elastic portions 53 are provided in this embodiment with respect toone structure 50, and each elastic portion 53 connects a portion of themass portion 51 and the fixed portion 52 in a plan view. In the seventhembodiment, the elastic portions 53 are connected to the corner portionsof the frame 573 of the mass portion 51, but are not limited thereto,and may be positioned at any position as long as the mass portion 51 canbe displaced with respect to the fixed portion 52. In FIG. 22, aconfiguration in which the mass portion 51 can be displaced in theY-axis direction is adopted. In the illustration, each of the elasticportions 53 has a meandering shape in a plan view and includes a firstportion extending along the X-axis direction and a second portionextending along the Y-axis direction. The shape of the drive portion 54is not limited to the illustrated shape as long as a configuration inwhich the drive portion 54 is elastically deformable in a desireddriving direction (Y-axis direction in the seventh embodiment).

Eight drive portions 54 are provided for one structure 50, and eachdrive portion 54 is connected to a portion of the mass portion 51extending along the Y-axis direction. Specifically, the four driveportions 54 are positioned on the +X side of the mass portion 51, andthe remaining four drive portions 54 are positioned on the −X side ofthe mass portion 51. Each drive portion 54 has a tooth shape including atrunk portion extending from the mass portion 51 in the X-axis directionand a plurality of branch portions extending from the trunk portion inthe Y-axis direction.

Eight fixed drive portions 55 and eight fixed drive portions 56 areprovided for each structure 50, respectively, and respective fixed driveportions 55 and 56 are fixed to the upper surface 23 of the substratedescribed above. In addition, the fixed drive portions 55 and 56 havetooth shapes corresponding to the drive portion 54, and are provided soas to sandwich the driving portion 54 therebetween.

Each of the detection portions 571 and 572 is a plate-shaped memberhaving a rectangular shape in a plan view, which is disposed inside themass portion 51 and is connected to the mass portion 51 by the beam 58.The detection portions 571 and 572 can rotate (displace) around arotation axis J4, respectively.

The fixed detection portion 59 (fixed detection electrode) faces thedetection portions 571 and 572. Further, the fixed detection portion 59is separated from the detection portions 571 and 572.

In addition, the mass portion 51, the elastic portion 53, the driveportion 54, a portion of the fixed drive portion 55, a portion of thefixed drive portion 56, the detection portions 571 and 572, and the beam58 having the configuration described above are provided above thesubstrate and are separated from the substrate 2.

The structure 50 as described above is collectively formed by patterninga conductive silicon substrate doped with impurities such as phosphorusand boron by etching.

As the constituent material of the fixed detection portion 59, forexample, aluminum, gold, platinum, indium tin oxide (ITO), ZnO (zincoxide), or the like can be used.

Although not illustrated, the fixed portion 52, the fixed drive portion55, the fixed drive portion 56, the fixed detection portion 59 a, andthe fixed detection portion 59 b are electrically connected to wiringsand terminals (not illustrated), respectively. These wirings andterminals are provided on a substrate, for example.

The configuration of the gyro sensor element 500 has been brieflydescribed as above. A gyro sensor element 500 having such aconfiguration can detect the angular velocity ωx as follows.

First, when a drive voltage is applied between the drive portion 54 andthe fixed drive portions 55 and 56 included in the gyro sensor element500, an electrostatic attractive force periodically changing inintensity occurs between the fixed drive portions 55 and 56 and thedrive portion 54. With this configuration, each drive portion 54vibrates in the Y-axis direction with elastic deformation of eachelastic portion 53. In this case, the plurality of drive portions 54included in the structure 50 a and the plurality of drive portions 54included in the structure 50 b vibrate (drive vibration) in oppositephases in the Y-axis direction.

When the angular velocity ωx is applied to the gyro sensor element 500in a state where the drive portion 54 vibrates in the Y-axis directionas described above, the Coriolis force acts and the detection portions571 and 572 are displaced around a rotation axis J4. In this case, thedetection portions 571 and 572 included in the structure 50 a and thedetection portions 571 and 572 of the structure 50 b are displaced inopposite directions. For example, when the detection portions 571 and572 included in the structure 50 a are respectively displaced in the+Z-axis direction, the detection portions 571 and 572 included in thestructure 50 b are respectively displaced in the −Z-axis direction.Further, when the detection portions 571 and 572 included in thestructure 50 a are respectively displaced in the −Z-axis direction, thedetection portions 571 and 572 included in the structure 50 b arerespectively displaced in the +Z-axis direction.

As the detection portions 571 and 572 displace (detect vibration) inthis manner, a distance between the detection portions 571 and 572 andthe fixed detection portion 59 changes. As the distance changes, theelectrostatic capacitance between the detection portions 571 and 572 andthe fixed detection portion 59 changes. The angular velocity ωx appliedto the gyro sensor element 500 can be detected based on the amount ofchange in the electrostatic capacitance.

Although the X-axis angular velocity sensor 112 is described, the sameapplies to the Y-axis angular velocity sensor 114.

Eighth Embodiment

Next, an eighth embodiment will be described. Hereinafter, differencesfrom the first to seventh embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose of the first to seventh embodiments, and redundant descriptionthereof will be omitted. The eighth embodiment is an embodiment of aphysical quantity sensor mounted on the multi-axis inertial sensor 17 inthe second embodiment, which corresponds to the X-axis accelerationsensor 122 and the Y-axis acceleration sensor 124 in the firstembodiment.

A physical quantity sensor 600 illustrated in FIG. 23 is an accelerationsensor capable of detecting acceleration Ax in the X-axis direction.Such a physical quantity sensor 600 includes a base portion 602 and anelement portion 604 which is provided in the base portion 602 andmeasures acceleration Ax (physical quantity) in the X-axis direction.The element portion 604 includes a fixed electrode 64 attached to thebase portion 602, a movable member 65 displaceable in the X-axisdirection (a first direction which is a detection axis direction of aphysical quantity) with respect to the base portion 602, and movableelectrodes 66 provided on the movable member 65. The fixed electrode 64includes a first fixed electrode 641 and a second fixed electrode 642arranged side by side along the Y-axis direction (a second directionwhich is a direction crossing the detection axis (orthogonal to thedetection axis in the eighth embodiment)).

The first fixed electrode 641 includes a first stem portion 643 and aplurality of first fixed electrode fingers 645 which are provided onboth sides of a first stem portion 643 in the Y-axis direction (seconddirection) and of which a longitudinal direction is along the seconddirection. In addition, the second fixed electrode 642 includes a secondstem portion 644 and a plurality of second fixed electrode fingers 646which are provided on both sides in the Y-axis direction (seconddirection) from the second stem portion 644 and of which a longitudinaldirection is along the second direction. The movable electrode 66includes a first movable electrode 661 and a second movable electrode662 arranged side by side along the Y-axis direction (second direction).At least a portion of the first movable electrode 661 includes aplurality of first movable electrode fingers 663 which are positioned onboth sides of the first stem portion 643 in the Y-axis direction (seconddirection), of which the longitudinal direction is along the seconddirection, and which face the first fixed electrode fingers 645 in theX-axis direction (first direction) At least a portion of the secondmovable electrode 662 includes a plurality of second movable electrodefingers 664 which are positioned on both sides of the second stemportion 644 in the Y-axis direction (second direction), of which thelongitudinal direction is along the second direction, and which face thesecond fixed electrode fingers 646 in the X-axis direction (firstdirection). With such a configuration, the first and second fixedelectrode fingers 645 and 646 and the first and second movable electrodefingers 663 and 664 can be respectively shortened while maintaining theelectrostatic capacitance between the first movable electrode finger 663and the first fixed electrode finger 645 and the electrostaticcapacitance between the second movable electrode finger 664 and thesecond fixed electrode finger 646 sufficiently large. For that reason,the physical quantity sensor 600 in which the electrode fingers 645,646, 663, and 664 are hard to be broken and which has excellent impactresistance is obtained.

Although the X-axis acceleration sensor 122 is described, the sameapplies to the Y-axis acceleration sensor 124.

Ninth Embodiment

Next, a ninth embodiment will be described. Hereinafter, differencesfrom the first to eighth embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose in the first to eighth embodiments, and redundant descriptionthereof will be omitted. The ninth embodiment is an embodiment of thephysical quantity sensor mounted on the multi-axis inertial sensor 17 inthe second embodiment, which is the Z-axis angular velocity sensor 116in the first embodiment.

FIG. 24 is a schematic plan view of a physical quantity sensor 700 of aninth embodiment. A movable body 720 includes a first movable member 720a and a second movable member 720 b. The movable body 720 includes thefirst movable member 720 a on one side in a direction orthogonal to arotation axis, the second movable member 720 b on the other side in thedirection orthogonal to the rotation axis, and a fifth beam and a sixthbeam connecting the first movable member 720 a and the second movablemember 720 b, in a plan view, with the rotation axis as a boundary, andan opening portion 726 is disposed between the fifth beam and the sixthbeam in a plan view, and the third beam connects the first beam and thefifth beam, and the fourth beam connects the second beam and the sixthbeam.

The first movable member 720 a is positioned on one side (−X-axisdirection side in the illustrated example) of a support axis Q in a planview (viewed from the Z-axis direction). The second movable member 720 bis positioned on the other side (+X-axis direction side in theillustrated example) of the support axis Q in a plan view.

In a case where acceleration in the vertical direction (for example,gravitational acceleration) is applied to the movable body 720,rotational moment (moment of force) is generated in each of the firstmovable member 720 a and the second movable member 720 b. Here, in acase where rotational moment (for example, counterclockwise rotationalmoment) of the first movable member 720 a and rotational moment of thesecond movable member 720 b (for example, clockwise rotational moment)are balanced, inclination of the movable body 720 does not change andacceleration cannot be detected. Accordingly, the movable body 720 isdesigned so that the rotational moment of the first movable member 720 aand the rotational moment of the second movable member 720 b are notbalanced and the movable body 720 has a predetermined inclination whenthe acceleration in the vertical direction is applied.

In the physical quantity sensor 700, by disposing the support axis Q ata position deviated from the center (center of gravity) of the movablebody 720 (by making the distances from the support axis Q to the tipends of the first movable member 720 a and the second movable member 720b different), the first movable member 720 a and the second movablemember 720 b have different masses.

That is, the mass of the movable body 720 is different between one side(first movable member 720 a) and the other side (second movable member720 b) with the support axis Q as a boundary. In the illustratedexample, the distance from the support axis Q to an end face 723 of thefirst movable member 720 a is greater than the distance from the supportaxis Q to an end face 724 of the second movable member 720 b. Inaddition, the thickness of the first movable member 720 a is equal tothe thickness of the second movable member 720 b. Accordingly, the massof the first movable member 720 a is larger than the mass of the secondmovable member 720 b.

As such, since the first movable member 720 a and the second movablemember 720 b have different masses, when the acceleration in thevertical direction is applied, the rotational moment of the firstmovable member 720 a and the rotational moment of the second movablemember 720 b cannot be balanced. Accordingly, when acceleration in thevertical direction is applied, it is possible to cause the movable body720 to have a predetermined inclination.

Although not illustrated, by disposing the support axis Q at the centerof the movable body 720 and making the thicknesses of the first movablemember 720 a and the second movable member 720 b different from eachother, the first movable member 720 a and the second movable member 720b may have different masses from each other. Even in such a case, whenthe acceleration in the vertical direction is applied, a predeterminedinclination can be generated in the movable body 720.

The movable body 720 is provided apart from a substrate 702. The movablebody 720 is provided above a recessed portion 11. A gap is providedbetween the movable body 720 and the substrate 702.

With this configuration, the movable body 720 can swing.

The movable body 720 includes a first movable electrode 721 and a secondmovable electrode 722 which are provided with the support axis Q as aboundary. The first movable electrode 721 is provided on a first movablemember 720 a.

The second movable electrode 722 is provided on a second movable member720 b.

The first movable electrode 721 is a portion of the movable body 720that overlaps with a first fixed electrode 750 in a plan view. The firstmovable electrode 721 forms an electrostatic capacitance C1 between thefirst movable electrode 721 and the first fixed electrode 750. That is,an electrostatic capacitance C1 is formed by the first movable electrode721 and the first fixed electrode 750.

The second movable electrode 722 is a portion of the movable body 720that overlaps with the second fixed electrode 752 in a plan view. Thesecond movable electrode 722 forms an electrostatic capacitance C2between the second movable electrode 722 and a second fixed electrode752. That is, the electrostatic capacitance C2 is formed by the secondmovable electrode 722 and the second fixed electrode 752. In thephysical quantity sensor 700, since the movable body 720 is made of aconductive material (silicon doped with impurities), the movableelectrodes 721 and 722 are provided.

That is, the first movable member 720 a functions as the first movableelectrode 721 and the second movable member 720 b functions as thesecond movable electrode 722.

The electrostatic capacity C1 and the electrostatic capacity C2 areconfigured to be equal to each other, for example, in a state where themovable body 720 is horizontal. The positions of the movable electrodes721 and 722 change according to movement of the movable body 720.Depending on the positions of the movable electrodes 721 and 722, theelectrostatic capacitances C1 and C2 change. A predetermined potentialis applied to the movable body 720 through a support portion 730.

In the movable body 720, a through-hole 725 penetrating the movable body720 is formed. With this configuration, it is possible to reduce theinfluence (air resistance) of air when the movable body 720 swings. Aplurality of through-holes 725 are formed. In the illustrated example, aplanar shape of the through-hole 725 is a square.

The movable body 720 is provided with an opening portion 726 penetratingthe movable body 720. The opening portion 726 is provided on the supportaxis Q in a plan view. In the illustrated example, the planar shape ofthe opening portion 726 is a rectangle.

A support portion 730 is provided on the substrate 702. The supportportion 730 is positioned in an opening portion 726. The support portion730 supports the movable body 720. The support portion 730 includes afirst fixed portion, a second fixed portion, a first beam 41, a secondbeam 42, a third beam 43, and a fourth beam 44.

The first fixed portion and the second fixed portion are fixed to thesubstrate 702. The first fixed portion and the second fixed portion areprovided so as to sandwich the support axis Q in a plan view. In theillustrated example, the first fixing portion is provided on the −X-axisdirection side of the support axis Q, and the second fixing portion isprovided on the +X-axis direction side of the support axis Q.

Tenth Embodiment

Next, a tenth embodiment will be described. Hereinafter, differencesfrom the first to ninth embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose of the first to ninth embodiments, and redundant descriptionthereof will be omitted. The tenth embodiment is an embodiment of themulti-axis inertial sensor 17 in the second embodiment.

Next, the physical quantity sensor according to the tenth embodimentwill be described with reference to FIGS. 25 and 26. FIG. 25 is a planview illustrating a schematic configuration of a physical quantitysensor 800 according to the tenth embodiment. For convenience ofexplanation, FIG. 25 illustrates a state in which a resin package isseen through. FIG. 26 is a cross-sectional view illustrating a schematicconfiguration of the physical quantity sensor 800 according to the tenthembodiment. In the following description, three axes orthogonal to eachother will be described using the X-axis, the Y-axis, and the Z-axis.Also, for the sake of convenience of explanation, the surface on the+Z-axis direction side, which is the sensor element side, is referred toas an upper surface and the surface on the opposite side to the −Z-axisdirection is referred to as a lower surface, in a plan view when viewedin the Z-axis direction.

As illustrated in FIGS. 25 and 26, the physical quantity sensor 800according to the tenth embodiment can be used as a six-axis sensorincluding a three-axis acceleration sensor capable of independentlymeasuring accelerations in the X-axis direction, the Y-axis direction,and the Z-axis direction and a three-axis angular velocity sensorcapable of independently measuring angular velocities in the X-axisdirection, the Y-axis direction, and the Z-axis direction.

Such a physical quantity sensor 800 includes a frame 871, an integratedcircuit (IC) 840 as a circuit element disposed on the frame 871, and anacceleration sensor element 820 and an angular velocity sensor element830 as sensor elements disposed one on each side of the IC 840 in the Xdirection in a plan view in the Z-axis direction, and a resin package884 covering these constituent parts. The frame 871 is attached to acircuit board 872 through a joining member (not illustrated). Theacceleration sensor element 820 and the angular velocity sensor element830 are attached to the upper surface of the frame 871 through a resinadhesive material 818 as a joining material. Further, the IC 840 isattached to the upper surface of the frame 871 through an adhesive layer841. In the tenth embodiment, the frame 871 corresponds to the substrateto which the acceleration sensor element 820 and the angular velocitysensor element 830 are attached.

The IC 840 includes, for example, a drive circuit for driving theacceleration sensor element 820 and the angular velocity sensor element830, a detection circuit for detecting acceleration in each of theX-axis, Y-axis, and Z-axis directions based on a signal from theacceleration sensor element 820, a detection circuit for detecting anangular velocity in each of the X-axis, Y-axis, and Z-axis directionsbased on a signal from the angular velocity sensor element 830, and anoutput circuit for converting signals from the respective detectioncircuits into predetermined signals and outputting the signals, and thelike.

The IC 840 includes a plurality of electrode pads (not illustrated) onits upper surface, and electrode pads are electrically connected toconnection terminals 875 and 877 provided on the circuit board 872through bonding wires 874 and 876. The other electrode pads areelectrically connected to terminals 878 of the acceleration sensorelement 820 through bonding wires 879. The other electrode pads areelectrically connected to terminals 881 of the angular velocity sensorelement 830 through bonding wires 882. With this configuration, the IC840 can control the acceleration sensor element 820 and the angularvelocity sensor element 830.

The acceleration sensor element 820 and the angular velocity sensorelement 830 are attached to the frame 871 by a resin adhesive material818.

On the lower surface of the circuit board 872, a plurality of externalterminals 885 are provided. The plurality of external terminals 885correspond to the connection terminals 875 and 877 provided on the uppersurface of the circuit board 872, respectively, and are electricallyconnected through internal wiring (not illustrated) or the like.

Eleventh Embodiment

Next, an eleventh embodiment will be described. Hereinafter, differencesfrom the first to tenth embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose of the first to tenth embodiments, and redundant descriptionthereof will be omitted. The eleventh embodiment is an embodiment of avehicle positioning device.

FIG. 27 is a block diagram illustrating the overall system of a vehiclepositioning device 3000 according to an eleventh embodiment. FIG. 28 isa diagram illustrating an action of the vehicle positioning device 3000illustrated in FIG. 27.

A vehicle positioning device 3000 illustrated in FIG. 27 is a devicewhich is used by being mounted on a vehicle and performs positioning ofthe vehicle. The vehicle is not particularly limited, and may be any ofa bicycle, an automobile (including a four-wheeled automobile and amotorcycle), a train, an airplane, a ship, and the like, but in theeleventh embodiment, the vehicle is described as a four-wheeledautomobile. The vehicle positioning device 3000 includes an inertiameasurement device 3100 (IMU), a computation processing unit 3200, a GPSreception unit 3300, a receiving antenna 3400, a position informationacquisition unit 3500, a position synthesis unit 3600, a processing unit3700, a communication unit 3800, and a display 3900. As the inertiameasurement device 3100, for example, the IMU 100 in the firstembodiment described above can be used.

The inertia measurement device 3100 includes a triaxial accelerationsensor 3110 and a triaxial angular velocity sensor 3120. The computationprocessing unit 3200 receives acceleration data from the accelerationsensor 3110 and angular velocity data from the angular velocity sensor3120, performs inertial navigation computation processing on these data,and outputs inertial navigation positioning data (data includingacceleration and attitude of the vehicle).

The GPS reception unit 3300 receives a signal (GPS carrier wave,satellite signal on which position information is superimposed) from theGPS satellite via the receiving antenna 3400. Further, the positioninformation acquisition unit 3500 outputs GPS positioning datarepresenting the position (latitude, longitude, altitude), speed,direction of the vehicle positioning device 3000 (vehicle) based on thesignal received by the GPS reception unit 3300. The GPS positioning dataalso includes status data indicating a reception state, a receptiontime, and the like.

Based on inertial navigation positioning data output from thecomputation processing unit 3200 and the GPS positioning data outputfrom the position information acquisition unit 3500, the positionsynthesis unit 3600 calculates the position of the vehicle, morespecifically, the position on the ground where the vehicle is traveling.For example, even if the position of the vehicle included in the GPSpositioning data is the same, as illustrated in FIG. 28, if the attitudeof the vehicle is different due to the influence of inclination of theground or the like, the vehicle is traveling at different positions onthe ground. For that reason, it is impossible to calculate an accurateposition of the vehicle with only GPS positioning data. Therefore, theposition synthesis unit 3600 calculates the position on the ground wherethe vehicle is traveling, using inertial navigation positioning data (inparticular, data on the attitude of the vehicle). This determination canbe made comparatively easily by computation using a trigonometricfunction (inclination θ with respect to the vertical direction).

The position data output from the position synthesis unit 3600 issubjected to predetermined processing by the processing unit 3700 anddisplayed on the display 3900 as a positioning result. Further, theposition data may be transmitted to the external device by thecommunication unit 3800.

The vehicle positioning device 3000 has been described as above. Asdescribed above, such a vehicle positioning device 3000 includes theinertia measurement device 3100, the GPS reception unit 3300 (receptionunit) that receives a satellite signal on which position information issuperimposed from a positioning satellite, the position informationacquisition unit 3500 (acquisition unit) that acquires positioninformation of the GPS reception unit 3300 based on the receivedsatellite signal, the computation processing unit 3200 (computationunit) that computes the attitude of the vehicle based on the inertialnavigation positioning data (inertia data) output from the inertiameasurement device 3100, and the position synthesis unit 3600(calculation unit) that calculates the position of the vehicle bycorrecting position information based on the calculated attitude. Withthis configuration, the effect of the inertia measurement device 3100which is the IMU 100 can be achieved, and the vehicle positioning device3000 with high reliability can be obtained.

In the above description, although description is made by using theglobal positioning system (GPS) as a satellite positioning system, otherglobal navigation satellite system (GNSS) may be used. For example, oneor more of satellite positioning systems among satellite positioningsystems such as European geostationary-satellite navigation overlayservice (EGNOS), quasi zenith satellite system (QZSS), global navigationsatellite system (GLONASS), GALILEO, beidou navigation satellite system(Bei Dou) may be used. Also, a stationary satellite type satellite-basedaugmentation system (SBAS) such as wide area augmentation system (WAAS)or European geostationary-satellite navigation overlay service (EGNOS)may be utilized in at least one of the satellite positioning systems.

Twelfth Embodiment

Next, a twelfth embodiment will be described. Hereinafter, differencesfrom the first to eleventh embodiments will be mainly described, and thesame reference numerals are given to the same constituent elements asthose of the first to eleventh embodiments, and redundant descriptionthereof will be omitted. The twelfth embodiment is an embodiment of anelectronic device.

FIG. 29 is a perspective view illustrating an electronic deviceaccording to the twelfth embodiment. A smartphone 1200 (mobile phone)illustrated in FIG. 29 is one to which the electronic device accordingto the invention is applied. In the smartphone 1200, the sensor unit 160in the second embodiment, and the control circuit 1210 (control unit)that performs control based on detection signals output from the sensorunit 160 are incorporated. Detection data (angular velocity data)measured by the sensor unit 160 is transmitted to the control circuit1210, and the control circuit 1210 can recognize the attitude andbehavior of the smartphone 1200 from the received detection data, changea display image displayed on the display unit 1208, generate an alarmsound or sound effect, or drive the vibration motor to vibrate the mainbody.

Such a smartphone 1200 (electronic device) has the sensor unit 160 andthe control circuit 1210 (control unit) that performs control based ondetection signals output from the sensor unit 160.

Thirteenth Embodiment

Next, a thirteenth embodiment will be described. Hereinafter,differences from the first to twelfth embodiments will be mainlydescribed, and the same reference numerals are given to the sameconstituent elements as those of the first to twelfth embodiments, andredundant description thereof will be omitted. The thirteenth embodimentis an embodiment of an electronic device.

FIG. 30 is a perspective view illustrating an electronic deviceaccording to the thirteenth embodiment. A digital still camera 1300illustrated in FIG. 30 is an example of the electronic device. Thedigital still camera 1300 includes a case 1302, and a display 1310 isprovided on the back surface of the case 1302. The display 1310 isconfigured to perform display based on the image capturing signal by acharge coupled device (CCD), and functions as a finder that displays thesubject as an electronic image. Alight receiving unit 1304 including anoptical lens (image capturing optical system), the CCD, and the like isprovided on the front side (the back side in the figure) of the case1302. When a photographer confirms the subject image displayed on thedisplay 1310 and presses a shutter button 1306, the image capturingsignal of the CCD at that time is transferred and stored in the memory1308. In the digital still camera 1300, the sensor unit 160 of thesecond embodiment and a control circuit 1320 (control unit) thatperforms control based on detection signals output from the sensor unit160 are incorporated. The sensor unit 160 is used for camera shakecorrection, for example.

Such a digital still camera 1300 (electronic device) includes the sensorunit 160 in the second embodiment and the control circuit 1320 (controlunit) that performs control based on detection signals output from thesensor unit 160. For that reason, the effect of the sensor unit 160 canbe achieved, and high reliability can be exhibited.

In addition to the personal computer and mobile phone and the digitalstill camera, the electronic device of the thirteenth embodiment can beapplied to, for example, a smartphone, a tablet terminal, a clock(including smart watch), an ink jet type discharging device (forexample, an ink jet printer), a laptop personal computer, a TV, awearable terminals such as HMD (head mounted display), a video camera, avideo tape recorder, a car navigation device, a pager, an electronicdatebook (including a datebook with communication function), anelectronic dictionary, a calculator, an electronic game machines, a wordprocessor, a work station, a videophone, a security TV monitor, anelectronic binoculars, a POS terminal, medical equipment (for example,electronic clinical thermometer, blood pressure monitor, blood glucosemeter, electrocardiogram measurement device, ultrasonic diagnosticdevice, electronic endoscope), a fish finder, various measuringinstruments, mobile terminal base station equipment, instruments (forexample, instruments of vehicles, aircraft, and ships), a flightsimulator, a network server, and the like.

Fourteenth Embodiment

Next, a fourteenth embodiment will be described. Hereinafter,differences from the first to thirteenth embodiments will be mainlydescribed, and the same reference numerals are given to the sameconstituent elements as those of the first to thirteenth embodiments,and redundant description thereof will be omitted. The fourteenthembodiment is an embodiment of a portable electronic device.

FIG. 31 is a plan view illustrating a portable electronic deviceaccording to the fourteenth embodiment. FIG. 32 is a functional blockdiagram illustrating a schematic configuration of the portableelectronic device illustrated in FIG. 31.

A watch type activity meter 1400 (active tracker) illustrated in FIG. 31is a wristwatch device which is a type of the portable electronicdevice. The activity meter 1400 is attached to a part (subject) such asthe user's wristwatch by a band 1401. The activity meter 1400 includes adisplay 1402 for digital display and can perform wireless communication.The sensor unit 160 in the second embodiment is incorporated in theactivity meter 1400 as an acceleration sensor 1408 for measuringacceleration and an angular velocity sensor 1409 for measuring angularvelocity.

The activity meter 1400 includes a case 1403 in which the accelerationsensor 1408 and the angular velocity sensor 1409 are accommodated, aprocessing unit 1410 which is accommodated in the case 1403 and is forprocessing output data from the acceleration sensor 1408 and the angularvelocity sensor 1409, the display 1402 accommodated in the case 1403,and a translucent cover 1404 covering the opening of the case 1403. Abezel 1405 is provided outside the translucent cover 1404. A pluralityof operation buttons 1406 and 1407 are provided on the side surface ofthe case 1403.

As illustrated in FIG. 32, the acceleration sensor 1408 measuresacceleration in each of the three axis directions which intersect(ideally orthogonal to) each other, and outputs a signal (accelerationsignal) according to the magnitude and direction of the detectedthree-axis acceleration. An angular velocity sensor 1409 measuresangular velocity in each of the three axis directions intersecting(ideally orthogonal to) each other, and outputs a signal (angularvelocity signal) according to the magnitude and direction of thedetected three-axis angular velocity.

In the liquid crystal display (LCD) constituting the display 1402,depending on various detection modes, for example, position informationusing a GPS sensor 1411 and a geomagnetic sensor 1412, exerciseinformation such as the amount of movement, the amount of exercise usingthe acceleration sensor 1408 and the angular velocity sensor 1409,biometric information such as a pulse rate using a pulse sensor 1413 orthe like, and time information such as current time, and the like aredisplayed. The environmental temperature using a temperature sensor 1414can also be displayed.

A communication unit 1415 performs various controls for establishingcommunication between a user terminal and an information terminal (notillustrated). The communication unit 1415 is configure to include atransceiver compatible with the short range wireless communicationstandard such as, for example, a Bluetooth (registered trademark)(including BTLE: Bluetooth Low Energy), Wireless Fidelity (Wi-Fi)(registered trademark), Zigbee (registered trademark), near fieldcommunication (NFC), ANT+(registered trademark) or the like, and aconnector compatible with a communication bus standard such as theuniversal serial bus (USB) or the like.

The processing unit 1410 (processor) is constituted by, for example, amicro processing unit (MPU), a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), or the like. Theprocessing unit 1410 executes various processing based on the programstored in a storing unit 1416 and a signal input from an operation unit1417 (for example, operation buttons 1406 and 1407). Processing by theprocessing unit 1410 includes data processing for each output signal ofthe GPS sensor 1411, the geomagnetic sensor 1412, a pressure sensor1418, the acceleration sensor 1408, the angular velocity sensor 1409,the pulse sensor 1413, the temperature sensor 1414, and the clockingunit 1419, display processing for causing the display 1402 to display animage, sound output processing for causing a sound output unit 1420 tooutput sound, communication processing for performing communication withthe information terminal via the communication unit 1415, and Powercontrol processing for supplying power from a battery 1421 to each unit,and the like.

Such an activity meter 1400 can have at least the following functions.

1. Distance: Measure the total distance from the start of measurementwith highly accurate GPS function.2. Pace: Display a current running pace from pace distance measurement.3. Average speed: Calculate an average speed and display the averagespeed from the start of running to the present.4. Altitude: Measure and display altitude with GPS function.5. Stride: Measure and display the stride even in a tunnel where GPSradio waves do not reach.6. Pitch: Measure and display the number of steps per minute.7. Heart rate: The heart rate is measured and displayed by the pulsesensor.8. Gradient: Measure and display the gradient of the ground in trainingand trail runs in the mountains.9. Auto lap: Automatically perform lap measurement when running for afixed distance set in advance or for a fixed time.10. Exercise consumption calorie: Display calorie consumption.11. Step count: Display the total number of steps from the start of theexercise.

Such an activity meter 1400 (portable electronic device) includes thephysical quantity sensors such as the acceleration sensor 1408 and anangular velocity sensor 1409, the case 1403 accommodating the physicalquantity sensors, the processing unit 1410 which is accommodated in thecase 1403 and performs processing output data from the physical quantitysensor, the display 1402 accommodated in the case 1403, and thetranslucent cover 1404 covering the opening portion of the case 1403.

As described above, the activity meter 1400 includes the GPS sensor 1411(satellite positioning system), and can measure a moving distance and amovement trajectory of the user. For that reason, a highly convenientactivity meter 1400 can be obtained.

The activity meter 1400 can be widely applied to a running watch, arunner's watch, a runner's watch for multiple sports such as duathlonand triathlon, an outdoor watch, and a GPS watch on which a satellitepositioning system such as the GPS is mounted.

Fifteenth Embodiment

Next, a fifteenth embodiment will be described. Hereinafter, differencesfrom the first to fourteenth embodiments will be mainly described, andthe same reference numerals are given to the same constituent elementsas those of the first to fourteenth embodiments, and redundantdescription thereof will be omitted. The fifteenth embodiment is anembodiment of a vehicle.

FIG. 33 is a perspective view illustrating a configuration of anautomobile which is an example of a vehicle in the fifteenth embodiment.

As illustrated in FIG. 33, the sensor unit 160 in the second embodimentis incorporated in an automobile 1500, and for example, the attitude ofa vehicle body 1501 can be detected by the sensor unit 160. Thedetection signal of the sensor unit 160 is supplied to a vehicle bodyattitude control device 1502 as an attitude control unit for controllingthe attitude of the vehicle body and the vehicle body attitude controldevice 1502 can measure the attitude of the vehicle body 1501 based onthe signal, control hardness of the suspension according to thedetection result, and control brakes of the individual wheels 1503. Inaddition, the sensor unit 160 can be widely applied to an electroniccontrol unit (ECU) such as a keyless entry, an immobilizer, a carnavigation system, a car air conditioner, an anti-lock braking system(ABS), an air bag, a tire pressure monitoring system (TPMS), an enginecontrol, a control device for inertial navigation for automaticoperation, a battery monitor of a hybrid vehicle or an electric vehicle,and the like.

In addition to the examples described above, the sensor unit 160 can beused for attitude control of a biped walking robot and a train, remotecontrol of a radio control airplane, a radio control helicopter, adrone, and the like, or attitude control of an autonomous flying object,attitude control of an agricultural machine, a construction machine, andthe like, for example. As described above, in realizing attitude controlof various vehicles, the sensor unit 160 and respective control units(not illustrated) are incorporated.

Since such a vehicle includes the sensor unit 160 and the control unit(not illustrated) in the second embodiment, the vehicle has excellentreliability.

Sixteenth Embodiment

A sixteenth embodiment is an embodiment that allows automatic operationin the vehicle 1500 of the fifteenth embodiment.

An advanced driver assistance systems (ADAS) locator used for theautomatically operated vehicle 1500 illustrated in FIG. 33 includes, inaddition to an inertial sensor including a sensor module 1610, a globalnavigation satellite system (GNSS) receiver, and a map database storingmap data. The ADAS locator measures a traveling position of the vehiclein real time by combining a positioning signal received by the GNSSreceiver and a measurement result of the inertial sensor. The ADASlocator reads the map data from the map database. An output from theADAS locator including the sensor module 1610 is input to an automaticoperation control unit 1620. The automatic operation control unit 1620controls at least one of acceleration, braking, and steering of thevehicle 1500 based on the output (including a detection signal from thesensor module 1610) from the ADAS locator.

FIG. 34 is a block diagram illustrating a system 1600 related anadvanced driver assistance systems (ADAS) locator. A switcher 1630switches execution or non-execution of automatic operation in theautomatic operation control unit 1620 based on change in the output(including change in the detection signal from the sensor module 1610)from the ADAS locator. The switcher 1630 outputs a signal for switchingfrom execution of the automatic operation to non-execution of theautomatic operation to the control unit 1620, for example, in a case ofabnormality in which detection capability of the sensor (including thesensor module 1610) in the ADAS locator is deteriorated.

The entire disclosure of Japanese Patent Application No. 2018-042387,filed Mar. 8, 2018, is expressly incorporated by reference herein.

What is claimed is:
 1. An inertial measurement unit comprising: when thethree axes orthogonal to each other are the X-axis, Y-axis, and Z-axis,an angular velocity sensor and an acceleration sensor, wherein theangular velocity sensor outputs a first angular velocity signal relatedto an angular velocity around the X axis, a second angular velocitysignal related to an angular velocity around the Y axis, and a thirdangular velocity signal related to an angular velocity around the Zaxis, wherein, when a bias error of the first angular velocity signal isBx [deg/sec], a bias error of the second angular velocity signal is setto By [deg/sec], and a bias error of the third angular velocity signalis Bz [deg/sec],Bz<Bx, andBz<By are satisfied.
 2. The inertial measurement unit according to claim1, whereinBz<0.5×Bx, andBz<0.5×By are satisfied.
 3. The inertial measurement unit according toclaim 1, wherein, when the Allan variance of the first angular velocitysignal is set as BISx [deg/hour], the Allan variance of the secondangular velocity signal is set as BISy [deg/hour], and the Allanvariance of the third angular velocity signal is set as BISz [deg/hour],BISz<0.5×BISx, andBISz<0.5×BISy are satisfied.
 4. The inertial measurement unit accordingto claim 3, whereinBISx>5,BISy>5, andBISz<2.5 are satisfied.
 5. The inertial measurement unit according toclaim 1, whereinBx>1140 [deg/hour],By >1140 [deg/hour], andBz<570 [deg/hour] are satisfied.
 6. The inertial measurement unitaccording to claim 1, wherein a structure of the Z-axis angular velocitysensor that detects the angular velocity around the Z-axis is differentfrom a structure of the X-axis angular velocity sensor that detects theangular velocity around the X-axis and a structure of the Y-axis angularvelocity sensor that detects the angular velocity around the Y-axis. 7.The inertial measurement unit according to claim 6, wherein the X-axisangular velocity sensor and the Y-axis angular velocity sensor detectthe angular velocity based on the amount of change in the electrostaticcapacitance.
 8. The inertial measurement unit according to claim 7,wherein the X-axis angular velocity sensor and the Y-axis angularvelocity sensor are Si-MEMS type angular velocity sensors.
 9. Theinertial measurement unit according to claim 6, wherein the Z-axisangular velocity sensor detects the angular velocity based on the changein frequency.
 10. The inertial measurement unit according to claim 9,wherein the Z-axis angular velocity sensor is a quartz crystal gyrosensor.
 11. The inertial measurement unit according to claim 6, whereinthe X-axis angular velocity sensor is configured to include Ngx sensorelements, the Y-axis angular velocity sensor is configured to includeNgy sensor elements, the Z-axis angular velocity sensor is configured toinclude Ngz sensor elements, andNgz>Ngx, andNgz>Ngy are satisfied.
 12. The inertia measurement device according toclaim 11, wherein Ngz≥2 is satisfied.
 13. A vehicle positioning devicecomprising: the inertial measurement unit according to claim 1, acomputation processing unit that calculates based on the angularvelocity data and acceleration data output from the inertial measurementunit, and a receiver that receives a satellite signal from the satellitepositioning system, a position information acquisition unit thatreceives a signal from the receiver, and a position synthesis unit thatcalculates the position based on the inertial data output from thearithmetic processing unit and the positioning data from the positioninformation acquisition unit.
 14. The vehicle positioning deviceaccording to claim 13, wherein outputs at least one of attitude,direction, position, and speed.
 15. The vehicle positioning deviceaccording to claim 14, wherein the position includes at least one oflatitude, longitude, and altitude.
 16. A system comprising: a vehiclepositioning device according to claim 14, and an automatic operationcontrol unit, wherein the automatic operation control unit controls atleast one of acceleration, braking, and steering based on the outputsignal of the vehicle positioning device.
 17. The system according toclaim 16, wherein execution or non-execution of the automatic operationis controlled based on the output signal of the vehicle positioningdevice.
 18. A vehicle comprising: the inertial measurement unitaccording to claim 1; and an attitude control device that controlsattitude based on the output signal of the inertial measurement unit.